Dielectric devices and methods of fabrication

ABSTRACT

Self-aligned liquid crystal materials and structures are disclosed. The structures can exhibit piezoelectric and flexoelectric properties.

FIELD

The present invention relates to dielectric devices fabricated usingmesogenic compounds and to methods of fabricating dielectric devicesusing mesogenic compounds. The materials and methods can be used tofabricate piezoelectric and flexoelectric devices.

BACKGROUND

Piezoelectric and flexoelectric properties play an important role inmany applications, such as sensors, actuators, and energy generators. Apiezoelectric material can have an electrical field induced when ahomogeneous strain is applied, and materials exhibiting flexoelectricitycan have a spontaneous electrical polarization when induced by a straingradient. Unlike piezoelectricity which requires structures with noinversion symmetry, flexoelectricity can emerge even in centrosymmetricmaterials due to the inhomogeneous strain locally breaking inversionsymmetry.

Several polymers exhibit piezoelectric and flexoelectric responses, suchas polyvinylidene fluoride (PVDF) and polyamides. The polymercrystallites can be oriented by poling using a high electric field at anelevated temperature. Poling can be difficult to control and can resultin burning and charring of the polymeric film or coating.

SUMMARY

According to the present invention, polymerizable compositions comprise:a solvent; and a combination of polymerizable mesogenic monomers.

According to the present invention, dielectric devices comprise adielectric layer, wherein the dielectric layer is prepared from thepolymerizable composition according to the present invention.

According to the present invention, parts comprise a dielectric deviceaccording to the present invention.

According to the present invention, methods of preparing a dielectriclayer, comprising: aligning a surface; applying the polymerizablecomposition according to the present invention to the aligned surface,wherein the polymerizable composition comprises a combination ofpolymerizable mesogenic monomers; allowing the applied combination ofpolymerizable mesogenic monomers to align; and polymerizing the alignedcombination of polymerizable mesogenic monomers to form a dielectriclayer.

According to the present invention, dielectric layers are prepared bymethods according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Those skilled in the art will understand that the drawings describedherein are for illustration purposes only. The drawings are not intendedto limit the scope of the present disclosure.

FIG. 1 shows the flexoelectric response for three-point bending of adielectric layer provided by the present disclosure on an aluminumsubstrate with 0.01% strain at 2 Hz.

FIG. 2A shows the flexoelectric response of a device according to thepresent invention before an applied impact.

FIG. 2B shows the flexoelectric response of a device according to thepresent invention in response to an impact.

DETAILED DESCRIPTION

For purposes of the following description, it is to be understood thatembodiments provided by the present disclosure may assume variousalternative variations and step sequences, except where expresslyspecified to the contrary. Moreover, other than in the examples, orwhere otherwise indicated, all numbers expressing, for example,quantities of ingredients used in the specification and claims are to beunderstood as being modified in all instances by the term about.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired properties to beobtained. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges encompassed therein. For example, arange of 1 to 10 is intended to include all sub-ranges between (andincluding) the recited minimum value of about 1 and the recited maximumvalue of about 10, that is, having a minimum value equal to or greaterthan about 1 and a maximum value of equal to or less than about 10.Also, in this application, the use of or means and/or unlessspecifically stated otherwise, even though and/or may be explicitly usedin certain instances.

Reference is now made to certain compounds, compositions, and methods ofthe present invention. The disclosed compounds, compositions, andmethods are not intended to be limiting of the claims. To the contrary,the claims are intended to cover all alternatives, modifications, andequivalents.

Cured layers provided by the present disclosure can exhibitflexoelectric properties and can produce an electrical signal inresponse to a force and/or mechanical actuation in response to anelectric field. A layer includes films and coatings, where a coatingrefers to an outer layer.

In the direct flexoelectric effect, an applied force induces stressgradients within a structure, leading to an electrical signal generatedin response to the stress gradient. The electrical signal is aflexoelectric signal. Unlike the piezoelectric effect, the flexoelectriceffect requires a stress gradient. A structure can undergo a bending orflexural deformation on application of the force. Electrodes may belocated so as to collect the flexoelectric signal, for example, locatedproximate regions of a stress gradient.

In the converse flexoelectric effect, application of an electrical fieldinduces electrical field gradients within the structure. Theseelectrical field gradients induce an actuating force through theflexoelectric effect, in this example the converse effect. In this case,electrodes can be located so that an electrical field gradient isgenerated.

The flexoelectric effect relates to an electric polarization induced bya strain gradient within a material, and the converse effect is a strainin the material induced by an electric field gradient. A flexoelectricmaterial can be centrosymmetric, which would seem to rule out anypiezoelectric effect.

The flexoelectric effect is defined by the relationship: P₁=μ_(ijkl) (∂S_(ij)/∂X_(k)); where μ_(ijkl) are the fourth rank polar tensorflexoelectric coefficients, S_(ij) is the elastic strain components.X_(k) is the direction of the gradient in S, and P₁ is the inducedelectric polarization.

For flexoelectricity there is also a converse effect, i.e. there is anelastic stress generated by an electric field gradient defined by therelationship: T_(ij)=μ_(ijkl) (∂E_(k)/∂ X_(l)); where E_(k) is theelectric field, xl the direction of the gradient in E, and T_(ij) theinduced stress.

For the direct effect in the MKS system, units for μ are coulombs/meter(C/m), and for the converse effect the units are Newton/volt (N/V),which are equivalent because the direct and converse flexoelectriceffects are thermodynamically identical.

Cured layers provided by the present disclosure can exhibitpiezoelectric properties. When stress is applied to a piezoelectricmaterial layer, electrical polarization by which opposite charges appearon both end faces of the piezoelectric material layer in proportion tothe applied stress results. And, when a piezoelectric material is placedin an electric field, the piezoelectric layer exhibits a property(piezoelectric effect) in which strain is generated in proportion to theapplied electric field. Specifically, in the case of a piezoelectriclayer a large piezoelectric effect appears via polarization caused byorientation of the dipole moment in the oriented polymer. When thepiezoelectric material layer is subjected to application of energy suchas heat, in response to this, a level of spontaneous polarization insidethe piezoelectric layer is altered.

Materials and methods for fabricating piezoelectric and flexoelectriclayers that can be aligned without poling are desired.

A polymerizable layer comprising mesogenic compounds provided by thepresent disclosure can self-align on an oriented substrate without theuse of poling methods and can be polymerized to form thin piezoelectricand flexoelectric layers.

Methods provided by the present disclosure can comprise aligning asubstrate surface by rubbing, coating the aligned surface with acomposition comprising a polymerizable mesogenic compound or combinationof polymerizable mesogenic-containing compounds, allowing the mesogeniccompounds to self-align, and curing the polymerizable mesogeniccompounds to provide a thin layer exhibiting piezoelectric and/orflexoelectric properties.

A dielectric device prepared from self-aligned polymerizable mesogeniccompounds can comprise an electrically conductive layer, an alignmentlayer overlying the substrate, a dielectric layer comprising polymerizedmesogenic compounds, and an overlying electrically conductive layer.

An electrically conductive material can comprise a material that isintrinsically electrically conductive or may comprise a layer of anelectrically conductive material overlying an electrically insulatingsubstrate.

A substrate can include any suitable substrate such as, for example, ametal, an alloy, a composite, a ceramic, glass, or a polymer. Asubstrate can be electrically conductive or a surface of the substratecan include a layer or coating of an electrically conductive material.For example, an electrically conductive coating can comprise indium tinoxide (ITO).

A substrate on which the dielectric layer is applied can be any suitablethickness. For example, the substrate can be a flexible sheet orflexible layer.

A substrate surface onto which a liquid crystal composition is appliedcan be characterized by an RMS smoothness/roughness, for example, fromscanning confocal microscopy or use profilometry.

A surface of the substrate can comprise an alignment layer. An alignmentlayer can comprise a thin layer of material that generates alignedphysical features such as aligned grooves when a mechanical force isapplied to the alignment layer such as by rubbing or buffing the thinlayer.

An alignment layer can be applied to an electrically conductivesubstrate or to an electrically conductive layer overlying a substratesurface. An alignment layer can be applied, for example, by dipping,brushing, rolling, spraying, wiping, or by any other suitable method. Analignment layer can be characterized by a thickness, for example, from 5μm to 100 μm, from 5 μm to 50 μm, or from 5 μm to 25 μm.

Examples of suitable alignment layer materials include alcohols such aspolyvinyl alcohol, triacetate cellulose, and polyimides. The materialscomprising the alignment layer can be applied as a solution and allowedto drying before generating alignment features using mechanical force.

Alignment features can be generated on the alignment layer by rubbing,buffing, or other suitable method. For example, alignment features canbe generated on the alignment layer by wiping a felt cloth or rotatingrubbing wheel across the surface of the alignment layer.

A surface can also be aligned by grooving or using photo-alignmentmethods.

After the alignment layer has been oriented, a dielectric compositioncomprising a polymerizable mesogenic material can be applied to thealigned surface of the alignment layer.

A dielectric composition can include a solvent, a polymerizablemesogenic compound, and a surfactant. For photopolymerizable liquidcrystal compositions, a composition can comprise a photoinitiator. Forthermally-activated polymerizable liquid crystal compositions, acomposition can comprise a thermal initiator.

Suitable solvents can dissolve the solid components of the polymerizabledielectric composition, are compatible with the surface to which thedielectric composition is applied, and can uniformly disperse the solidcomponents across an aligned substrate surface. A suitable solvent canalso be capable of evaporating after application and alignment of themesogenic compounds.

A dielectric composition can comprise, for example, from 20 wt % to 60wt % of a solvent or a combination of solvents, from 25 wt % to 55 wt %,from 30 wt % to 50 wt %, or from 35 wt % to 45 wt % of a solvent or acombination of solvents, where wt % is based on the total weight of thecomposition.

In dielectric compositions a solvent can be a polar solvent. Examples ofsuitable polar solvents include anisole.

Examples of suitable solvents include propylene glycol monomethyl etheracetate and derivatives thereof, acetone, amyl propionate, anisole,benzene, butyl acetate, cyclohexane, dialkyl ethers of ethylene glycol,e.g., diethylene glycol dimethyl ether and their derivatives, diethyleneglycol dibenzoate, dimethyl sulfoxide, dimethyl formamide,dimethoxybenzene, ethyl acetate, isopropyl alcohol, methylcyclohexanone, cyclopentanone, methyl ethyl ketone, methyl isobutylketone, methyl propionate, propylene carbonate, tetrahydrofuran,toluene, xylene, 2-methoxyethyl ether, 3-propylene glycol methyl ether,and combinations of any of the foregoing.

Dielectric compositions can comprise a mesogenic compound or combinationof mesogenic compounds.

Suitable mesogenic compounds are disclosed, for example, in U.S. Pat.No. 8,628,685, in U.S. Application Publication No. 2010/0014010, and inU.S. Application Publication No. 2009/0323012, each of which isincorporated by reference in its entirety.

A mesogenic compound comprises a mesogenic portion and a flexibleportion.

The mesogenic portion of a compound can comprise a rigid moiety whichaligns with other mesogenic portions in a composition comprisingmesogenic compounds, thereby aligning the mesogenic compounds in onedirection. The rigid portion of the mesogen may comprise a rigidmolecular structure, such as a mono or polycyclic ring structure,including, for example, mono or polycyclic aromatic ring structures.Examples of mesogens include the mesogenic compounds disclosed in Demuset al., Flussige Kristalle in Tabellen, VEB Deutscher Verlag furGrundstoffindustrie, Leipzig, 1974 and Flussige Kristalle in TabellenII, VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1984.Mesogenic compounds may also include one or more flexible portions. Theone or more flexible portions may impart fluidity to the mesogeniccompound. Mesogenic compounds may exist in a non-ordered state or in anordered or aligned state. Mesogenic compounds in a non-ordered state canadopt an essentially random orientation such that there is no generalorientation to the mesogenic compound. Mesogenic compounds in theordered or aligned state can adopt an orientation in which the mesogenicportions of the compounds are at least partially aligned throughout thecomposition.

Mesogenic compounds can comprise at least one mesogen unit, at least onereactive group, and at least one flexible linking group which may be,for example, from 1 atomic bond to 500 atomic bonds in linear length. Amesogenic compound can comprise one reactive group or two reactivegroups.

Mesogenic compounds can comprise compounds having the structure ofFormula (1):

P-L_(w)-(-M¹-X)_(z)   (1)

In mesogenic compounds of Formula (1), each X can independentlycomprise:

(i) a group —R;

(ii) a group -(L)_(y)-R;

(iii) a group -(L)-R;

(iv) -(L)_(w)-Q;

(v) a group having the structure of Formula (2):

-L_(y)-M²-L_(w)-P   (2)

(vi) -L_(y)-P; or

(vii) -L_(w)-[(L)_(w)-P]_(y).

In compounds of Formula (1), each P can comprise a reactive group. Areactive group refers to an atom, bond, or functional group that mayreact to form a bond, such as a covalent, polar covalent, or ionic bondwith another molecule. For example, a reactive group may react with agroup, react with a co-monomer, or a reactive group on a developingpolymer such that the structure corresponding to Formula (1) or aresidue thereof is incorporated into the polymer. Each reactive group Pcan independently comprise, for example, aziridinyl, hydrogen, hydroxyl,aryl, alkyl, alkoxy, amino, alkylamino, alkylalkoxy, alkoxyalkoxy,nitro, polyalkyl ether, C₁₋₆ alkyl, C₁₋₆ alkoxy(C₁₋₆)alkyl,polyethyleneoxy, polypropyleneoxy, ethanediyl, acrylate, methacrylate,2-chloroacrylate, 2-phenylacrylate, acryloylphenylene, acrylamide,methacrylamide, 2-chloroacrylamide, 2-phenylacrylamide, oxetane, epoxy,glycidyl, cyano, isocyanato, thiol, thioisocyanato, itaconic acid ester,vinyl ether, vinyl ester, a styrene derivative, siloxane, ethyleneiminederivatives, carboxylic acid, alkene, maleic acid derivatives, fumaricacid derivatives, unsubstituted cinnamic acid derivatives, cinnamic acidderivatives that are substituted with at least one of methyl, methoxy,cyano and halogen, or substituted or unsubstituted chiral or non-chiralmonovalent or divalent groups chosen from steroid radicals, terpenoidradicals, alkaloid radicals and mixtures thereof, wherein thesubstituents can independently be alkyl, alkoxy, amino, cycloalkyl,alkylalkoxy, fluoroalkyl, cyano, cyanoalkyl, cyanoalkoxy or combinationsof any of the foregoing. A reactive group P can comprise a polymerizablegroup, wherein the polymerizable group may be any functional groupcapable of participating in a polymerization reaction.

For example, polymerization reactions include addition polymerization inwhich free radicals serve as the initiating agents that react with thedouble bond of a monomer by adding to it on one side at the same timeproducing a new free electron on the other side; condensationpolymerization in which two reacting molecules combine to form a largermolecule with elimination of a small molecule, such as a water molecule;and oxidative coupling polymerization. A reactive group P may be anunsubstituted or substituted ring opening metathesis polymerizationprecursor. Examples of suitable polymerizable groups include hydroxyl,acryloxy, methacryloxy, 2-(acryloxy)ethylcarbamyl,2-(methacryloxy)ethylcarbamyl, isocyanato, aziridine, allylcarbonate,and epoxy groups such as oxiranylmethyl. A reactive group P can comprisea plurality of reactive groups. For example, reactive group P cancomprise from 2 to 4 reactive groups. Having multiple reactive groups onP may provide for more effective incorporation into a polymer or providefor cross-linking between individual polymer strands. Examples of asuitable reactive group P comprising multiple reactive groups includediacryloyloxy(C₁₋₆)alkyl, diacryloyloxyaryl; triacryloyloxy(C₁₋₆)alkyl,triacryloyloxyaryl, tetraacryloyloxy(C₁₋₆)alkyl, tetraacryloyloxyaryl,dihydroxy(C₁₋₆)alkyl, trihydroxy(C₁₋₆)alkyl, tetrahydroxy(C₁₋₆)alkyl,diepoxy(C₁₋₆)alkyl, diepoxyaryl, triepoxy(C₁₋₆)alkyl, triepoxyaryl,tetraepoxy(C₁₋₆)alkyl, tetraepoxyaryl, diglycidyloxy(C₁₋₆)alkyl,diglycidyloxyaryl; triglycidyloxy(C₁₋₆)alkyl, triglycidyloxyaryl,tetraglycidyloxy(C₁₋₆)alkyl, and tetraglycidyloxyaryl.

In mesogenic compounds of Formula (1), each group Q can comprise, forexample, hydroxyl, amine, alkenyl, alkynyl, azido, silyl, silylhydride,oxy(tetrahydro-2H-pyran-2-yl), isocyanato, thiol, thioisocyanato,carboxylic acid, carboxylic ester, amide, carboxylic anhydride, or acylhalide. The group Q may act as a reactive group such that a mesogeniccompound comprising at least one group Q may be incorporated into thebackbone of a polymer or copolymer. For example, Q may be apolymerizable group, such as those described herein, including hydroxyl,acryloxy, methacryloxy, 2-(acryloxy)ethylcarbamyl,2-(methacryloxy)ethylcarbamyl, isocyanato, thiol, thioisocyanato,aziridine, allylcarbonate, carboxylic acid or carboxylic acidderivative, or epoxy, e.g., oxiranylmethyl. As used herein, the terms(meth)acryloxy and (meth)acryloyloxy are used interchangeably and referto a substituted or unsubstituted prop-2-en-1-oyloxy structure.

In mesogenic compounds of Formula (1), the groups -L-, -(L)_(y)- or-(L),- represent linking groups having a linear length of from 1 to 500atomic bonds, such as from 1 to 200, from 1 to 100, or from 1 to 50atomic bonds. That is, for the general structure F-L-E, the longestlinear length of the linking group between groups F and E (where groupsF and E may each generally represent any of groups P, R, Q, X or amesogen) can range from 1 to 500 bonds (inclusive of the interveningatoms). It should be understood that when discussing the linear lengthof the linking group, the length of the linking group may be calculatedby determining the length of each of the bonds in the linear sequenceand the distance occupied by the various intervening atoms in the linearsequence of the linking group and totaling the values. The longestlinear sequence of bonds may be at least 25 bonds between the linkedgroups. The longest linear sequence of bonds may be at least 30 bonds.The longest linear sequence of bonds may be at least 50 bonds. A linkinggroup of at least 25 bonds can improve the solubilities of theadditives, such as the photochromic compounds in compositions comprisingthe mesogenic compounds; may provide for faster or improved alignmentproperties of the compositions comprising the mesogenic compounds;and/or may lower the viscosity of a composition comprising the mesogeniccompound.

Each group -L- can independently be selected from a single bond, apolysubstituted, monosubstituted or unsubstituted spacer including aryl,(C₁₋₃₀)alkyl, (C₁₋₃₀)alkylcarbonyloxy, (C₁₋₃₀)alkylamino, (C₁₋₃₀)alkoxy,(C₁₋₃₀)perfluoroalkyl, (C₁₋₃₀)perfluoroalkoxy, (C₁₋₃₀)alkylsilyl,(C₁₋₃₀)dialkylsiloxyl, (C₁₋₃₀)alkylcarbonyl, (C₁₋₃₀)alkoxycarbonyl,(C₁₋₃₀)alkylcarbonylamino, (C₁₋₃₀)alkylaminocarbonyl,(C₁₋₃₀)alkylcarbonate, (C₁₋₃₀)alkylaminocarbonyloxy,(C₁₋₃₀)alkyloxycarbonylamino, (C₁₋₃₀)alkylurethane, (C₁₋₃₀)alkylurea,(C₁₋₃₀)alkylthiocarbonylamino, (C₁₋₃₀)alkylaminocarbonylthio,(C₂₋₃₀)alkene, (C₁₋₃₀)thioalkyl, (C₁₋₃₀)alkylsulfone, and(C₁₋₃₀)alkylsulfoxide, wherein each substituent can independently be,for example, (C₁₋₅)alkyl, (C₁₋₅)alkoxy, fluoro, chloro, bromo, cyano,(C₁₋₅)alkanoate ester, isocyanato, thioisocyanato, or phenyl.

The variable w may be an integer from 1 to 26, y may be an integer from2 to 25, and z can be 1 or 2.

It should be noted that when more than one L group occurs in sequence,for example in the structure -(L)_(y)- or -(L)_(w)- where y and/or w isan integer greater than 1, then the adjacent L groups may or may nothave the same structure. That is, for example, in a linking group havingthe structure -(L)₃- or -L-L-L- (i.e., where y or w is 3), each group-L- can independently be any of the groups L recited herein and theadjacent -L- groups may or may not have the same structure. For example,-L-L-L- may represent —(C₁₋₃₀)alkyl-(C₁₋₃₀)alkyl-(C₁₋₃₀)alkyl- (i.e.,where each occurrence of -L- is represented by (C₁₋₃₀)alkyl, where eachadjacent (C₁₋₃₀)alkyl group may have the same or different number ofcarbons in the alkyl group). As another example, -L-L-L- may represent-aryl-(C₁₋₃₀)alkylsilyl-(C₁₋₃₀)alkoxy—(i.e., where each occurrence of-L- differs from the adjacent groups -L-). Thus, the structure of(L)_(y) or (L)_(w) should be understood as covering all possiblecombinations of the various sequences of the linking groups -L-,including those where some or all of the adjacent -L- groups are thesame and where all the adjacent -L- groups are different.

In mesogenic compounds of Formula (1), the group R can comprise an endgroup such as hydrogen, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy, C₁₋₁₈ alkoxycarbonyl,C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, poly(C₁₋₁₈ alkoxy), or astraight-chain or branched C₁₋₁₈ alkyl group that is unsubstituted orsubstituted with cyano, fluoro, chloro, bromo, or C₁₋₁₈ alkoxy, orpoly-substituted with fluoro, chloro, or bromo.

In mesogenic compounds of Formula (1), the groups M¹ and M² representmesogenic groups and can each independently be a rigid straight rod-likeliquid crystal group, a rigid bent rod-like liquid crystal, or a rigiddisc-like liquid crystal group. The structures for M¹ and M² may be anysuitable mesogenic group such as, for example, any of those recited inDemus et al., Flussige Kristalle in Tabellen, VEB Deutscher Verlag furGrundstoffindustrie, Leipzig, 1974 or Flussige Kristalle in Tabellen II,VEB Deutscher Verlag fur Grundstoffindustrie, Leipzig, 1984.

Mesogen groups M¹ and M² may independently have a structure of Formula(3):

-[S¹]_(c)-[G¹-[S²]_(d)]_(d′)-[G²-[S³]_(e)]_(e′)-[G³-[S⁴]_(f)]_(f′)-S⁵-  (3)

In mesogenic groups of Formula (3) each of G¹, G², and G³ mayindependently comprise a divalent group such as: an unsubstituted or asubstituted aromatic group, an unsubstituted or a substituted alicyclicgroup, an unsubstituted or a substituted heterocyclic group, andmixtures thereof, wherein substituents can be, for example, thiol,amide, hydroxy(C₁₋₁₈)alkyl, isocyanato(C₁₋₁₈)alkyl, acryloyloxy,acryloyloxy(C₁₋₁₈)alkyl, halogen, C₁₋₁₈ alkoxy, poly(C₁₋₁₈ alkoxy),amino, amino(C₁₋₁₈)alkylene, C₁₋₁₈ alkylamino, di-(C₁₋₁₈)alkylamino,C₁₋₁₈ alkyl, C₂₋₁₈ alkene, C₂₋₁₈ alkyne, C₁₋₁₈ alkyl(C₁₋₁₈)alkoxy, C₁₋₁₈alkoxycarbonyl, C₁₋₁₈ alkylcarbonyl, C₁₋₁₈ alkyl carbonate, arylcarbonate, perfluoro(C₁₋₁₈)alkylamino, di-(perfluoro(₁₋₈)alkyl)amino,C₁₋₁₈ acetyl, C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, isocyanato, amido,cyano, nitro, a straight-chain or branched C₁₋₁₈ alkyl group that ismono-substituted with cyano, halo, or C₁₋₁₈ alkoxy, or poly-substitutedwith halo, and a group comprising one of the following formulae:M(T)_((t-1)) and M(OT)_((t-1)), where M can be aluminum, antimony,tantalum, titanium, zirconium, or silicon, T can be an organofunctionalradical, an organofunctional hydrocarbon radical, an aliphatichydrocarbon radical or an aromatic hydrocarbon radical, and t is thevalence of M.

In mesogenic groups of Formula (3), each of c, d, e, and f mayindependently be an integer ranging from 0 to 20, inclusive; and each ofd′, e′ and f′ can independently be an integer from 0 to 4 provided thata sum of d′+e′+f′ is at least 1.

In mesogenic groups of Formula (3), the groups S can be spacer groupssuch that each of groups S¹, S², S³, S⁴, and S⁵ can independentlyselected from one of groups (i), (ii), or (iii):

(i) —(CH₂)_(g)-, —(CF₂)_(h)-, —Si(CH₂)_(g), and h is a whole number from1 to 16 inclusive;

(ii) —N(Z), —C(Z)═C(Z), —C(Z)=N, —C(Z′)₂-C(Z′)₂, or a single bond,wherein each Z is independently hydrogen, C₁₋₆ alkyl, cycloalkyl, oraryl, and each Z′ is independently C₁₋₆ alkyl, cycloalkyl, or aryl; or

(iii) —O—, —C(O)—, —CH═CH—, —N═N—, —S—, —S(O)—, —S(O)₂-, —S(O)₂-O—,—O—S(O)₂-O— or straight-chain or branched C₁₋₂₄ alkylene residue, whereC₁₋₂₄ alkylene residue can be unsubstituted, mono-substituted by cyanoor halo, or poly-substituted by halo; provided that when two spacerunits comprising heteroatoms are linked together the spacer units arelinked so that heteroatoms are not directly bonded to each other andwhen S¹ and S⁵ are linked to another group, they are linked so that twoheteroatoms are not directly bonded to each other.

In mesogenic groups of Formula (3), each of c, d, e, and f canindependently be an integer ranging from 1 to 20, inclusive; and each ofd′, e′ and f′ can independently be 0, 1, 2, 3, and 4, provided that thesum of d′+e′+f′ is at least 1.

In mesogenic groups of Formula (3), each of c, d, e, and f can beindependently be an integer from 0 to 20, inclusive; and each of d′, e′and f′ can independently be 0, 1, 2, 3, or provided that the sum ofd′+e′+f′ is at least 2.

In mesogenic groups of Formula (3), each of c, d, e, and f canindependently be an integer from 0 to 20, inclusive; and each of d′, e′and f′ can independently be 0, 1, 2, 3, or 4, provided that the sum ofd′+e′+f′ is at least 3.

In mesogenic groups of Formula (3), each of c, d, e, and f canindependently be an integer from 0 to 20, inclusive; and each of d′, e′and f′ can independently be 0, 1, 2, 3, or 4, provided that the sum ofd′+e′+f′ is at least 1.

In mesogenic compounds of Formula (1), when the group X is —R, then wcan be an integer from 2 to 25, and z can be 1; when the group X is-L_(y)-R, then w can be 1, y can be an integer from 2 to 25, and z canbe 1; when the group X is -(L)-R, then w can be an integer from 3 to 26,and z can be 2; when the group X is -L_(w)-Q, then if the group P inFormula (1) is Q, which may be the same or different that the othergroup Q, w can be 1, and z can be 1 and if the group P is other than thegroup Q (i.e., P is another group as defined herein), then each w canindependently be an integer from 1 to 26, and z can be 1; when the groupX is has the structure of Formula (2), (-L_(y)-M²-L_(w)-P_(y)), then wcan be 1, y can be an integer from 2 to 25, and z can be 1; when thegroup X is -(L)_(y)-P, then w can be 1, y can be an integer from 2 to26, and z can be 1, and -L_(y)- can comprise a linear sequence of atleast 25 bonds between the mesogen and P; and when the group X is-L_(w)-[(L)_(w)-P]_(y), then each w can be independently an integer from1 to 25, y can be an integer from 2 to 6, and z can be 1.

A mesogenic compound may be a functional mono-mesogenic compound (i.e.,a mesogenic compound that contains one mesogenic structure). Afunctional mono-mesogenic compound may have a structure of Formula (1),wherein the group X is —R, w is an of Formula (1), wherein the group Xis -L_(y)-R, w is 1,y is an integer from 2 to 25, and z is 1.

A mesogenic compound may be a functional bi-mesogenic compound (i.e., amesogenic compound that contains two mesogenic structures, which may bethe same or different). For example, a functional bi-mesogenic compoundcan have a long chain linking group between the two mesogenic units. Afunctional bi-mesogenic compound may have a structure of Formula (1),wherein the group X is -L-R, w is an integer from 3 to 26, and z is 2. Afunctional bi-mesogenic compound may have a structure of Formula (1),wherein the group X has the structure of Formula (2):

L_(y)-M²-L_(w)-P_(y)   (2)

where w is 1, y is an integer from 2 to 25, and z is 1.

A mesogenic compound may be a functional mono-mesogenic compound (i.e.,a mesogenic compound that contains one mesogenic structure). Forexample, a functional mono-mesogenic compound may have a of Formula (1),wherein the group X is -L_(w)-Q and if the group P in Formula (1) is Q,which may be the same or different than the other group Q, w is 1, and zis 1; and if the group P is other than the group Q, then each w isindependently and integer from 1 to 26 and z is 1. A mesogenic compoundwith this structure may contain two groups Q, which may be the same ordifferent, and may be reactive with one or more other monomeric unitswhich may react to form a copolymer. Thus, a mesogenic compound may be adi-functional monomer that may be incorporated into a polymer backbone.That is, the mesogenic group can be incorporated into a polymer backboneand be attached at each end to the formed polymer by the residues of thegroup(s) Q. The term residue refers to a group that remains afterreaction of a reactive group.

A functional mono-mesogenic compound may have a structure of Formula(1), wherein the group X is -L_(y)-P, w is 1, y is an integer from 2 to25, and z is 1; and -L_(y)- comprises a linear sequence of at least 25bonds between the mesogen and P. The group -L_(y)- can comprise a linearsequence of at least 50 bonds between the mesogen and P.

A mesogenic compound may have a structure of Formula (1) where the groupX is -L_(w)-[(L)_(w)-P]_(y), each w is independently an integer from 1to 25, y is an integer from 2 to 6, and z is 1. A mesogenic compound mayhave, for example, from 3 to 7 reactive groups P.

Mesogenic compounds provided by the present disclosure can provide curedlayers that exhibit piezoelectric and/or flexoelectric properties.

Mesogenic compounds provided by the present disclosure can comprise aliquid crystal monomer having the structure of Formula (4) or Formula(5):

R-M-L_(w)-P   (4)

R-L_(y)-M-L-P   (5)

The group P in monomers of Formula (4) and Formula (5) may be a reactivegroup such as those set forth in the listing for P herein and includinggroups comprising polymerizable groups, a plurality of reactive groups,or ring opening metathesis polymerization precursors.

The group Q in monomers of Formula (4) and Formula (5) may independentlybe any of those groups listed for group Q herein. Further, in monomersof Formula (4) and Formula (5), each group -L- may independently beselected from the listing of possible -L- groups set forth herein. Inmonomers of Formula (4) and Formula (5), the group R may be selectedfrom the listing of possible R groups set forth herein.

The mesogen component M¹ and M² in monomers of Formula (4) and Formula(5) may be a rigid straight rod-like liquid crystal group, a rigid bentrod-like liquid crystal group, or a rigid disc-like liquid crystalgroup, such as the mesogens set forth herein including those having thestructure of Formula (3):

-[S¹]_(c)-[G¹-[S² _(d)]_(d′)-[G²-[S³]_(e)]_(e′)-[G³-[S⁴]_(f)]_(f′)-S⁵-   (3)

where S¹, S², S³, S⁴, S⁵, G¹, G², G³, c, d, e, f, d′, e′, and f′ aredefined herein. In monomers of Formula (4) and Formula (5) w may be aninteger ranging from 2 to 25, and y may be an integer ranging from 2 to25.

Mesogenic compounds provided by the present disclosure includebi-mesogen liquid crystal monomers having the structure of Formula (6)and Formula (7):

P-L-M-L_(w)-M²-L-P   (6)

P-L-M¹-L_(w)(-L-P)(-M²-L-R)   (⁷)

In mesogenic compounds of Formula (6) and Formula (7), each P mayindependently comprise a reactive group such as any of those discloseherein including polymerizable groups, multiple reactive groups, or ringopening metathesis polymerization precursors. Each Q may independentlycomprise any of the groups for Q disclosed herein. In mesogeniccompounds of Formula (6) and Formula (7), each L may independentlycomprise any of the groups for L disclosed herein. In mesogeniccompounds of Formula (6) and Formula (7), each R may independentlycomprise any of the groups for R disclosed herein. The mesogen portionin mesogenic compounds of Formula (6) and Formula (7) may comprise rigidstraight rod-like liquid crystal groups, rigid bent rod-like liquidcrystal groups, rigid disc-like liquid crystal groups, or a combinationof any of the foregoing. Thus, M¹ and M² in compounds of Formula (6) andFormula (7) may independently comprise a mesogenic structure disclosedherein including, for example, the structure of Formula (3):

-[S¹]_(c)-[G¹-[S²]_(d)]_(d′)-[G²-[S³]_(e)]_(e′)-[G³-[S⁴]_(f)]_(f′)-S⁵-  (3)

where S¹, S², S³, S⁴, S⁵, G¹, G², G³, c, d, e, f, d′, e′, and f′ aredefined herein. In mesogenic compounds of Formula (6) and Formula (7) wmay be an integer from 2 to 25.

A mesogenic compound can comprise a bi-functional liquid crystal monomerrepresented by the structure of Formula (8):

P-L_(w)-M-L_(w)-Q   (8)

In mesogenic compounds of Formula (8), P can comprise a reactive group,such as a polymerizable group, a plurality of reactive groups, or ringopening metathesis polymerization precursors. If P is represented by thegroup Q, then w can be 1; and if P is other than Q, then each w canindependently be an integer from 1 to 26.

In mesogenic compounds of Formula (8), each group Q may independently beany of those groups listed for group Q herein. Further, in Formula (8),each group -L- may be independently chosen for each occurrence, whichmay be the same or different, from the listing of possible -L- groupsset forth herein. The mesogen component in Formula (8) may be a rigidstraight rod-like liquid crystal group, a rigid bent rod-like liquidcrystal group, or a rigid disc-like liquid crystal group, such as themesogens set forth herein including those having the structure ofFormula (3):

-[S¹]_(c)-[G¹-[S²]_(d)]_(d′)-[G²-[S³]_(e)]_(e′)-[G³-[S⁴]_(f)]_(f′)-S⁵-  (3)

where S¹, S², S³, S⁴, S⁵, G¹, G², G³, c, d, e, f, d′, e′, and f′ aredefined herein.

A mesogenic compound can comprise a liquid crystal monomer having thestructure of Formula (9):

P-L-M-L_(y)-P   (9)

In mesogenic compounds of Formula (9), each group P may independentlycomprise a reactive group such as those set forth in the listing for Pdescribed herein and including those P groups comprising polymerizablegroups, a plurality of reactive groups, or ring opening metathesispolymerization precursors. The group Q may independently be any of thosegroups listed for Q herein. Further, in Formula (9), each group -L- maybe independently chosen for each occurrence, which may be the same ordifferent, from the listing of possible -L- groups set forth herein. Themesogen component in Formula (9) may be a rigid straight rod-like liquidcrystal group, a rigid bent rod-like liquid crystal group, or a rigiddisc-like liquid crystal group, such as the mesogens set forth hereinincluding those having the structure of Formula (3):

-[S¹]_(c)-[G¹-[S²]_(d)]_(d′)-[G²-[S³]_(e)]_(e′)-[G³-[S⁴]_(f)]_(f′)-S⁵-  (3)

where S¹, S², S³, S⁴, S⁵, G¹, G², G³, c, d, e, f, d′, e′, and f′ aredefined herein. In addition, in Formula (9), y may be an integer rangingfrom 2 to 25. In mesogenic compounds of Formula (9), -L_(y)- cancomprise a linear sequence of at least 25 bonds between the mesogen andthe group P. In mesogenic compounds of Formula (9), -L_(y)- may comprisea linear sequence of at least 50 bonds between the mesogen and the groupP.

A mesogenic compound can have the structure of Formula (10):

P-L_(w)-M-L_(w)-(-L_(w)-P)_(y)   (10)

Mesogenic compounds of Formula (10) may comprise from 3 to 7 P groups,wherein each group P in Formula (10) may independently be a reactivegroup such as those set forth in the listing for P described herein andincluding those P groups comprising polymerizable groups, a plurality ofreactive groups, or ring opening metathesis polymerization precursors.The group Q may independently be any of those groups listed for group Qherein. In compounds of Formula (10), each group -L- may beindependently chosen for each occurrence, which may be the same ordifferent, from the listing of possible -L- groups set forth herein. Themesogen component in Formula (10) may be a rigid straight rod-likeliquid crystal group, a rigid bent rod-like liquid crystal group, or arigid disc-like liquid crystal group, such as the mesogens set forthherein including those having the structure of Formula (3):

-S₁]_(c)-[G₁-[S₂]_(d)]_(d′)-[G₂-[S₃]_(e)]_(e′)-[G₃-[S₄]_(f)]_(f′)-S₅-   (3)

where S¹, S², S³, S⁴, S⁵, G¹, G², G³, c, d, e, f, d′, e′, and f′ aredefined herein. In compounds of Formula (12), each w may independentlybe an integer from 1 to 25, and y may be an integer from 2 to 6.

Mesogenic compounds of Formula (1) and (4)-(10) can comprise a longflexible linking group between one or more portions of the compound. Forexample, linking groups -L_(y)- and/or -L_(w)- and in certain cases thegroup -L- (for example, when -L- comprises at least 25 linear bonds) maycomprise a long flexible linking group comprising a long linear sequenceof chemical bonds, ranging from 25 to 500 chemical bonds in length,between the two groups linked by the linking group. A linking group maycomprise a long linear sequence of chemical bonds ranging from 30 to 500chemical bonds in length between the two groups. A linking group maycomprise a long linear sequence of chemical bonds ranging from 50 to 500chemical bonds in length between the two groups. As used with referenceto the linking group, the chemical bonds in the linear sequence betweenthe groups linked by the linking group may be covalent or polar covalentchemical bonds, such as covalent or polar covalent σ-bonds and may alsoinclude one or more π-bonds (although the π-bonds are not included whencalculating the length of chemical bonds in the linear sequence).Further, it will be understood by those skilled in the art that thelinking group can also comprise those intervening atoms through whichthe linear sequence of bonds are associated.

Polymerizable mesogenic monomers can comprise a compound of Formula (1):

P-(L)_(w)-(M¹-X)_(z)   (1)

wherein,

-   -   a) each —X is independently:        -   i) a group —R;        -   ii) a group represented by -(L)_(y)-R;        -   iii) a group represented by -(L)-R;        -   iv) a group represented by -(L)_(w)-Q;        -   v) a group represented by a moiety of Formula (2):

-(L)^(y)-M²-(L)_(w)-P   (2)

-   -   -   vi) a group represented by -(L)_(y)-P; or        -   vii) a group represented by -(L)_(w)-[(L)_(w)-P]_(y);

    -   b) P comprises a reactive group;

    -   c) Q is selected from hydroxyl, amine, alkenyl, alkynyl, azido,        silyl, silylhydride, oxy(tetrahydro-2H-pyran-2-yl), thiol,        isocyanato, thioisocyanato, acryloxy, methacryloxy,        2-(acryloxy)ethylcarbamyl, 2-(methacryloxy)ethylcarbamyl,        aziridinyl, allylcarbonate, epoxy, carboxylic acid, carboxylic        ester, amide, carboxylic anhydride, and acyl halide;

    -   d) each L is independently selected from a single bond, a        polysubstituted, monosubstituted, unsubstituted or branched        spacer independently comprising aryl, (C₁₋₃₀)alkyl,        (C₁₋₃₀)alkylcarbonyloxy, (C₁₋₃₀)alkylamino, (C₁₋₃₀)alkoxy,        (C₁₋₃₀)perfluoroalkyl, (C₁₋₃₀)perfluoroalkoxy,        (C₁₋₃₀)alkylsilyl, (C₁₋₃₀)dialkylsiloxyl, (C₁₋₃₀)alkylcarbonyl,        (C₁₋₃₀)alkoxycarbonyl, (C₁₋₃₀)alkylcarbonylamino,        (C₁₋₃₀)alkylaminocarbonyl, (C₁₋₃₀)alkylcarbonate,        (C₁₋₃₀)alkylaminocarbonyloxy, (C₁₋₃₀)alkylaminocarbonylamino,        (C₁₋₃₀)alkylurea, (C₁₋₃₀)alkylthiocarbonylamino,        (C₁₋₃₀)alkylaminocarbonylthio, (C₂₋₃₀)alkene, (C₁₋₃₀)thioalkyl,        (C₁₋₃₀)alkylsulfone, or (C₁₋₃₀)alkylsulfoxide, wherein each        substituent is independently chosen from (C₁₋₅)alkyl,        (C₁₋₅)alkoxy, fluoro, chloro, bromo, cyano, (C₁₋₅)alkanoate        ester, isocyanato, thioisocyanato, and phenyl;

    -   e) R is selected from hydrogen, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy, C₁₋₁₈        alkoxycarbonyl, C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, poly(C₁₋₁₈        alkoxy), and a straight-chain or branched C₁₋₁₈ alkyl group that        is unsubstituted or substituted with cyano, fluoro, chloro,        bromo, or C₁₋₁₈ alkoxy, or poly-substituted with fluoro, chloro,        or bromo; and

    -   f) each of M¹ and M² independently comprise a rigid straight        rod-like liquid crystal group, a rigid bent rod-like liquid        crystal group, or a rigid disc-like liquid crystal group;

    -   wherein,        -   w is an integer from 1 to 26;        -   y is an integer from 2 to 25; and        -   z is 1 or 2;

    -   provided that when,        -   X is R, then w is an integer from 2 to 25, and z is 1;

    -   X is -(L)_(y)-R, then w is 1, y is an integer from 2 to 25, and        z is 1;        -   X is -(L)-R, then w is an integer from 3 to 26, and z is 2;        -   X is -(L)_(w)-Q; then if P is represented by the group Q,            then w is 1, and z is 1; and if P is other than the group Q,            then each w is independently an integer from 1 to 26 and z            is 1;        -   X is a moiety of Formula (2), -(L)_(y)-M²-(L)₁-P, then w is            1, y is an integer from 2 to 25, and z is 1;        -   X is -(L)_(y)-P, then w is 1, y is an integer from 2 to 25,            and z is 1 and -(L)_(y)- comprises a linear sequence of at            least 25 bonds between the mesogen and P; and        -   X is -(L)_(w)-[(L)_(w)-P]_(y), then each w is independently            an integer from 1 to 25, y is an integer from 2 to 6, and z            is 1.

Dielectric compositions provided by the present disclosure can comprisea single mesogenic compound or a combination of mesogenic compounds.

The mesogenic compounds can be polymerizable and have functional groupsreactive with functional groups of other mesogenic compounds in thedielectric composition.

Reactive groups of the mesogenic monomers can be selected as appropriatefor any suitable curing chemistry. For example, a suitable curingchemistry can comprise the reaction between thiol groups, and epoxy,alkenyl, or Michael acceptor groups.

The mesogenic compounds can be photopolymerizable such that themesogenic compounds comprise functional groups that are reactive whenthe composition comprising the mesogenic compounds is exposed to UVradiation. For example, photopolymerizable mesogenic compounds cancomprise terminal acrylate or methacrylate groups. A photopolymerizablemesogenic compound can comprise a single terminal (meth)acrylate groupor can comprise two terminal (meth)acrylate groups. Photopolymerizablegroups can also include thiol and alkenyl groups. Photopolymerizablemesogenic compounds having a single reactive group are referred to asmonofunctional photopolymerizable mesogenic compounds, andphotopolymerizable mesogenic compounds having two reactive groups arereferred to as difunctional photopolymerizable mesogenic compounds.

A suitable curing chemistry includes urethane and urea chemistries wherethe reactive groups can be isocyanate, amine, and hydroxyl groups.

The mesogenic compounds can be thermally-polymerizable such that themesogenic compounds comprise functional groups that are reactive whenthe composition comprising the mesogenic compounds is exposed to heatsuch as a temperature greater than 30° C., greater than 40° C., greaterthan 50° C., or greater than 60° C. For example, thermally-polymerizablemesogenic compounds can comprise terminal acrylate or methacrylategroups. A thermally-polymerizable mesogenic compound can comprise asingle terminal (meth)acrylate group or can comprise two terminal(meth)acrylate groups. Thermally-polymerizable groups can also includethiol and alkenyl groups. thermally-polymerizable mesogenic compoundshaving a single reactive group are referred to as monofunctionalthermally-polymerizable mesogenic compounds, and thermally-polymerizablemesogenic compounds having two reactive groups are referred to asdifunctional thermally-polymerizable mesogenic compounds.

Compositions provided by the present disclosure can comprise a mol %ratio of difunctional to monofunctional polymerizable mesogeniccompounds, for example, from 20 to 60, from 25 to 55, from 30 to 50, orfrom 35 to 45.

Mesogenic compounds provided by the present disclosure can have amolecular weight, for example, from 300 Daltons to 3,000 Daltons, from300 Daltons to 2,000 Daltons, from 300 Daltons to 1,500 Daltons, from300 Daltons to 1,000 Daltons, or from 400 Daltons to 800 Daltons, wheremolecular weight can be determined by gel permeation chromatographyusing polystyrene standards.

Specific examples of suitable mesogenic compounds include:

Dielectric compositions can comprise mesogenic Compounds (1)-(7), or acombination of any of the foregoing.

Other examples of suitable mesogenic compounds include the compoundsdisclosed in U.S. Application Publication No. 2010/0014010, which isincorporated by reference in its entirety, including any of thosedisclosed in Table 1 (U.S. Application Publication No. 2010/0014010)having at least one (meth)acrylate group, such as:

or a combination of any of the foregoing.

Dielectric compositions can comprise a combination of mesogeniccompounds having two reactive functional groups (difunctional mesogeniccompound), and mesogenic compounds having one reactive functional group(monofunctional mesogenic compound). A reactive functional group can bea photoreactive functional group such as an acrylate or methacrylategroup. A reactive functional group can be a photoreactive functionalgroup such as an acrylate or methacrylate group. The molar ratio ofdifunctional mesogenic compounds to monofunctional mesogenic compoundscan be, for example, from 2:1 to 1:1, from 1.8:1 to 1:1, from 1.6:1 to1:1, from 1.4:1 to 1:1 or from 1.2:1 to 1:1. A ratio of bifunctionalmesogenic compounds to monofunctional mesogenic compounds can beselected such that the polymerized mesogenic compounds on average formshort chains of two or three mesogenic compounds.

A dielectric composition can comprise, for example, from 40 wt % to 80wt % of a combination of polymerizable mesogenic monomers, from 45 wt %to 75 wt %, from 50 wt % to 70 wt %, or from 55 wt % to 65 wt % of acombination of polymerizable mesogenic monomers, such asphotopolymerizable mesogenic monomers, or thermally-initiated mesogenicmonomers, where wt % is based on the total weight of the composition.

Dielectric compositions may also comprise a surfactant or combination ofsurfactants.

Surfactants include materials such as wetting agents, anti-foamingagents, emulsifiers, dispersing agents, and leveling agents. Surfactantscan be anionic, cationic, or nonionic.

A dielectric composition provided by the present disclosure cancomprise, for example, from 0.001 wt % to 0.200 wt % of a surfactant orcombination of surfactants, from 0.0005 wt % to 0.5000 wt %, from 0.01wt % to 0.12 wt %, from 0.02 wt % to 0.10 wt % of a surfactant orcombination of surfactants, where wt % is based on the total weight ofthe composition.

Examples of suitable nonionic surfactants include ethoxylated alkylphenols, such as the IGEPAL® DM surfactants (Sigma Aldrich)oroctyl-phenoxypolyethoxyethanol available as TRITON® X-100 (SigmaAldrich), acetylenic diols such as 2,4,7,9-tetramethyl-5-decyne-4,7-diolavailable as SURFYNOL® 104 (Air Products), ethoxylated acetylenic diolssuch as SURFYNOL® 400 surfactants, and fluoro-surfactants such asFLUORAD® fluorochemical surfactants (3M). Examples of suitable cappednonionic surfactants include benzyl capped octyl phenol ethoxylatedavailable as TRITON® CF87, propylene oxide capped alkyl ethoxylates suchas PLURAFAC® RA surfactants (BASF), octylphenoxyhexadecylethoxy benzylether, polyether modified dimethylpolysiloxane copolymer available asBYK®-306 (Byk-Chemie). A surfactant can include a combination of any ofthe foregoing surfactants.

Dielectric compositions provided by the present disclosure can comprisea polymerization inhibitor to stabilize the reactive monomers andprevent spontaneous polymerization. For example, dielectric compositionsprovided by the present disclosure can comprise monomethyl etherhydroquinone (MEHQ, 4-hydroxy phenol) as a polymerization inhibitor.

Dielectric compositions can comprise, for example, from 0.001 wt % to0.200 wt % of a polymerization inhibitor or combination ofpolymerization inhibitors, from 0.0005 wt % to 0.5000 wt %, from 0.01 wt% to 0.12 wt %, from 0.02 wt % to 0.10 wt % of a polymerizationinhibitor or combination of polymerization inhibitors, where wt % isbased on the total weight of the composition.

Examples of suitable polymerization inhibitors include butylatedhydroxytoluene and butylhydroxytoluene (BHT).

Photopolymerizable compositions can be cured, for example, upon exposureto ultraviolet (UV) radiation. A photopolymerizable composition cancomprise a photoinitiator.

Dielectric compositions provided by the present disclosure can comprise,for example, from 0.01 wt % to 5 wt % of a photoinitiator or combinationof photoinitiators, from 0.05 wt % to 4 wt %, from 0.2 wt % to 3 wt %,or from 0.5 wt % to 2 wt % of a photoinitiator or combination ofphotoinitiators, where wt % is based on the total weight of thecomposition.

Examples of suitable photoinitiators include cleavage-typephotoinitiators and abstraction-type photoinitiators. Examples ofsuitable cleavage-type photoinitiators include acetophenones,α-aminoalkylphenones, benzoin ethers, benzoyl oximes, acylphosphineoxides and bisacylphosphine oxides and combinations of any of theforegoing. Examples of suitable abstraction-type photoinitiators includebenzophenone, Michler's ketone, thioxanthone, anthraquinone,camphorquinone, fluorone, ketocoumarin and combinations of any of theforegoing.

Polymerizable compositions provided by the present disclosure can bethermally activated. A thermally-activated polymerizable composition cancomprise a thermal initiator. Examples of suitable thermal initiatorsinclude azo compounds such as 4,4′-azobis(4-cyanovaleric acid),1,1′-azobis(cyclohexanecarbonitirle), azobisisobutyronitrile,2,2′-azobis(2-methylpropionamidine), and2,2′-azobis(2-methylpropionitrile; inorganic peroxides such as ammoniumpersulfate, hydroxymethanesulfinic acid, potassium persulfate, andsodium persulfate; and organic peroxides such as tert-butylhydroperoxide, cumene hydroperoxide,2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne,1,1-bis(tert-butylperoxy)cyclohexane,2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, benzoyl peroxide,2-butanone peroxide, and tert-butyl peroxide.

Polymerizable compositions provided by the present disclosure may notinclude a photoinitiator or a thermal initiator.

Dielectric compositions can comprise a drying agent to remove orsequester water. Examples of suitable drying agents include calciumchloride, calcium sulfate, magnesium sulfate, potassium carbonate,potassium hydroxide and sodium sulfate.

Dielectric compositions can be applied to a substrate surface or to acoating or film overlying a substrate surface. A substrate surface canfirst be cleaned, for example, by wiping with a volatile solvent such asacetone and dried with nitrogen gas. A substrate can also be cleanedwith a plasma such as an oxygen plasma.

A cleaned substrate surface can be planarized by applying a thin layerof a polymer coating. Examples of materials used as planarization layersinclude polyvinyl alcohol. A planarization layer can be applied, forexample, by spin coating or brushing.

An alignment layer can be applied to the substrate surface using, forexample, spin coating a material such as polyvinyl alcohol onto thesurface. An alignment layer can have a thickness, for example, less than100 nm, less than 50 nm, less than 25 nm, or less than 10 nm.

The alignment layer can be oriented, for example, by uni-directionallyrubbing the alignment layer.

After the alignment layer is oriented, a dielectric composition can beapplied to the aligned layer, for example, by spin coating, brushing orother suitable method capable of providing a layer having a thickness,for example, less than 200 μm, less than 100 μm, less than 75 μm, lessthan 25 μm, less than 20 μm, less than 15 μm, less than 10 μm, or lessthan 5 μm.

After application to an aligned surface, the mesogenic compounds in thecomposition self-align. The mesogenic compounds can be allowed toself-align at room temperature or at elevated temperature. Heat and/orvibration may be applied to facilitate alignment of the mesogeniccompounds. Heating the dielectric composition can also facilitatesolvent removal from the thin layer. The mesogenic compounds canself-align such that the long axis of the mesogenic compounds assumes anorientation that is generally parallel to the general direction oforientation of the surface. The mesogenic compounds will exhibit apiezoelectric and/or flexoelectric effect when the dipole moments of themesogenic compounds are aligned perpendicular to the surface.

The aligned dielectric composition can be heated to remove solvents, andthen exposed to UV radiation to cure the polymerizable liquid crystal.Any suitable UV source may be used at an appropriate UV flux sufficientto photopolymerize the liquid crystal monomers. Alternatively, analigned dielectric composition comprising a thermal initiator can beheated to polymerize the liquid crystal monomers. A cured layer providedby the present disclosure can be characterized by a thickness, forexample, less than 100 μm, less than 75 μm, less than 50 μm, less than25 μm, less than 10 μm, or less than 5 μm. A cured layer provided by thepresent disclosure can be characterized by a thickness from 1 μm to 100μm, from 5 μm to 100 μm, from 1 μm to 75 μm, from 1 μm to 50 μm, or from1 μm to 25 μm.

Cured dielectric layers provided by the present disclosure are thermosetmaterials.

Cured dielectric layers provided by the present disclosure can exhibitpiezoelectric and/or flexoelectric properties.

In certain uses, the piezo- and/or flexo-electric effect can be enhancedby post-processing treatment such as by annealing, stretching, and/orbiaxial-orientation.

Dielectric layers provided by the present disclosure may be used inpiezoelectric and flexoelectric devices such as sensors, actuators,energy harvesters, and electromechanical energy conversion devices.Dielectric layers provided by the present disclosure can be used inelectronic devices such as in transducers, sensors, actuators,ferroelectric memories, and in capacitors by electrical devices.

A dielectric layer provided by the present disclosure can comprise acoating on a substrate. The substrate may be of any suitable thicknessand rigidity. The dielectric layer may be applied as a coating to thesubstrate or may be a layer of a multi-layer structure.

A dielectric layer provided by the present disclosure can beelectrically connected with electrodes. The electrodes may beinterconnected to a portion of the dielectric layer. The electrodes canbe in the form of a thin film such that a dielectric layer provided bythe present disclosure is sandwiched between the two thin films formingthe electrodes. The electrodes may have any suitable shape, dimensionsor configuration. For example, the electrodes may be in the form of aninterdigitated comb pattern.

Dielectric layers provided by the present disclosure do not requirepoling and are polymerized. As a consequence the dielectric layerscannot be become depoled thermally, electrically, or mechanically.

EXAMPLES

Embodiments provided by the present disclosure are further illustratedby reference to the following examples, which describe the synthesis,properties, and uses of certain compositions comprising polymerizablemesogenic compounds, layers formed from the compositions, and devicesfabricated from the compositions. It will be apparent to those skilledin the art that many modifications, both to materials, and methods, maybe practiced without departing from the scope of the disclosure.

Examples 1-3 describe the preparation of the materials of the presentinvention. Example 4 describes the methods used to measure the meltingpoints and the liquid crystal phase transition temperatures of Examples1-3. These examples are also disclosed in U.S. Pat. No. 8,628,685, whichis incorporated by reference in its entirety.

The following abbreviations were used for the chemicals listed in theExamples and Figures:

Al(OiPr)₃ aluminum triisopropylate

DHP 3,4-dihydro-2H-pyran

DCC dicyclohexylcarbodiimide

DIAD diisopropyl azodicarboxylate

DMAP 4-dimethylaminopyridine

PPh₃ triphenyl phosphine

PPTS pyridine p-toluenesulfonate

NMP N-methylpyrrolidone

NMR proton nuclear magnetic resonance;

TBD 1,5,7-triazabicyclo[4.4.0]dec-5-ene

THF tetrahydrofuran

Example 1 Synthesis of Mesogenic Compounds

Step 1: To a reaction flask was added 4-hydroxybenzoic acid (20 g),3-chloro-1-propanol (34 g), N-methylpyrrolidone (NMP) (200 mL), andpotassium carbonate (50 g) and the mixture was vigorously stirred at110° C. for 4 hours. The resulting mixture was extracted using 1/1volume ratio of ethyl acetate/hexanes (1 L) and water (500 mL). Theseparated organic layer was washed several times with water to removeNMP and then dried over magnesium sulfate. After concentration, therecovered oil (40 g) was used directly in the next step.

Step 2: To a reaction flask was added the product from Step 1 (40 g),succinic anhydride (40 g), DMAP (0.5 g) and THF (200 mL) and theresulting mixture was refluxed for 4 hours. Extraction was done usingethyl acetate (1 L) and water (1 L). The organic layer was separated,dried over magnesium sulfate and concentrated. The resulting product waspurified by silica column separation using a mixture of ethylacetate/hexane (8/2 volume/volume (v/v)). A clear oil (36.6 g) wasobtained as the product. NMR showed that the product had a structureconsistent with4-(3-((4-(3-((3-carboxypropanoyl)oxy)propoxy)benzoyl)oxy)propoxy)-4-oxobutanoicacid.

Step 3: To a reaction flask was added 6-chloro-1-hexanol (51 g),methylene chloride (200 mL) and p-toluenesulfonic acid monohydride (0.5g). The mixture was stirred at room temperature. DHP (33.5 g) was addedthrough a dropping funnel over a 20 minute interval. The resultingmixture was stirred at room temperature for an hour and thenconcentrated. The recovered clear oil (79 g) was used directly in thenext step.

Step 4: To a reaction flask containing the product from Step 3 (78.2 g)was added ethyl 4-hydroxybenzoate (65 g), potassium carbonate (147 g)and NMP (700 mL). The mixture was stirred at 120° C. for six hours andthen poured to 1.5 L of water. The mixture was extracted with hexane(1.5 L). The separated organic layer was washed with water, dried overmagnesium sulfate and concentrated. The recovered clear oil (126.7 g)was used directly in the next step.

Step 5: To the reaction flask containing the product from Step 4 (126.7g) was added sodium hydroxide water solution (64 g of a 50 weightpercent solution based on the total weight of the solution), methanol(300 mL) and water (200 mL). The mixture was refluxed for 2 hours andmost of the methanol was removed using a rotary evaporator. Water (1.5L) was added to the resulting mixture and a clear solution was obtained.The pH of the solution was adjusted to −7 by the slow addition of 3M HCl(˜270 mL was used). A large amount of an undesired precipitate formed.The resulting mixture was extracted with ethyl acetate twice (500 mLeach time). The separated organic layer was washed with water, driedover magnesium sulfate and concentrated until solids started to form.Hexanes (1 L) was added to further crystallization of the product. Theresulting crystals were collected by filtration and dried in a vacuumoven. White crystals were obtained as the product (89.7 g). NMR showedthat the product had a structure consistent with4-(6-(tetrahydro-2H-pyran-2-yloxy)hexyloxy)benzoic acid.

Step 6: To a reaction flask was added 4-(trans-4-propylcyclohexyl)phenol(4.78 g), 4-(6-(tetrahydro-2H-pyran-2-yloxy)hexyloxy)benzoic acid (7.068g) from Step 5, N,N′-dicyclohexylcarbodiimide (5 g),4-dimethylaminopyridine (0.25 g) and methylene chloride (100 ml). Themixture was stirred at room temperature for 4 hours. The solid byproductthat formed was filtered off The resulting solution was concentrated andethanol (100 mL), 1,2-dichloroethane (100 mL) and pyridiniump-toluenesulfonate (1 g) were added. The resulting mixture was refluxedfor 2 days and then concentrated. The product was purified by silicacolumn separation using methylene chloride/acetone (50/1 v/v) followedby recrystallization from methanol. White crystals (6.47 g) wereobtained as the product. NMR showed that the product had a structureconsistent with 4-(trans-4-propylcyclohexyl)phenyl4-((6-hydroxyhexyl)oxy)benzoate.

Step 7: To a reaction flask was added 4-(trans-4-propylcyclohexyl)phenyl4-((6-hydroxyhexyl)oxy)benzoate (1.47 g) from Step 6,4-(3-((4-(3-((3-carboxypropanoyl)oxy)propoxy)benzoyl)oxy)propoxy)-4-oxo-butanoicacid (0.76 g) from Step 2, N,N′-dicyclohexylcarbodiimide (0.72 g),4-dimethylaminopyridine (0.03 g) and methylene chloride (20 mL). Themixture was stirred at room temperature for 4 hours. The solid byproductthat formed was filtered off. The solution was concentrated and theproduct was purified by silica column separation using methylenechloride/acetone (50/1 v/v) followed by recrystallization from a mixtureof methylene chloride/ethanol. A white solid (0.97 g) was obtained asthe product. NMR showed that the product had a structure consistent with1-{3-(4-(3-(4-(6-(4-(4-(4-propylcyclohexyl)phenoxycarbonyl)phenoxy)-hexyloxy)-4-oxobutanoyloxy)propyloxy)benzoyloxy)propyloxy}-4-{6-(4-(4-(trans-4-propylcyclohexyl)phenoxycarbonyl)phenoxy)hexyloxy)butane-1,4-dione.

Example 2 Synthesis of Mesogenic Compounds

Step 1: To a reaction flask was added 4-hydroxybenzoic acid (90 grams(g), 0.65 mole), ethyl ether (1000 mL) and p-toluenesulfonic acid (2 g).The resulting suspension was stirred at room temperature.3,4-Dihydro-2H-pyran (DHP) (66 g, 0.8 mole) was added to the mixture.The suspension turned clear soon after the addition of DHP and a whitecrystalline precipitate formed. The mixture was then stirred at roomtemperature overnight. The resulting precipitate was collected by vacuumfiltration and washed with ethyl ether. White crystals were recovered asthe product (90 g). NMR showed that the product had a structureconsistent with 4-(tetrahydro-2H-pyran-2-yloxy)benzoic acid.

Step 2: To a reaction flask was added4-(tetrahydro-2H-pyran-2-yloxy)benzoic acid (17 g) from Step 1,4-(trans-4-propylcyclohexyl)phenol (15.1 g), dicyclohexylcarbodiimide(DCC) (15.7 g), 4-dimethylaminopyridine (DMAP) (0.8 g) and methylenechloride (100 ml). The resulting mixture was stirred at room temperaturefor 2 hours. The resulting solid byproduct was filtered off The solutionwas concentrated and methanol (100 mL), 1,2-dichloroethane (100 mL) andpyridine p-toluenesulfonate (PPTS) (2 g) were added. The resultingmixture was heated to reflux and maintained at reflux for 6 hours.Solvent was removed and the resulting product was purified by silicacolumn separation using a mixture of ethyl acetate/hexane (2/8 v/v). Awhite solid was obtained as the product (16 g). NMR showed that theproduct had a structure consistent with4-(trans-4-propylcyclohexyl)phenyl-4-hydroxybenzoate.

Step 3: To a reaction flask was added the product of Step 2 (4.98 g),polycaprolactone diol (2.6 g, Aldrich catalogue number 189405),triphenyl phosphine (3.86 g), THE (40 mL) and diisopropylazodicarboxylate (2.98 g). The resulting mixture was stirred at roomtemperature for 20 hours. After concentration, a silica gel flash columnseparation using ethyl acetate hexanes mixture was used to collect themajor components of the products. A white solid was recovered as theproduct (3.2 g). NMR showed that the product had a structure consistentwith2,2′-bis(6-(6-(4-(4-(trans-4-propylcyclohexyl)phenoxycarbonyl)phenoxy)hexanoyloxy)-6-hexanoyloxy)diethyletherwith each n having an average distribution of 2.2.

Example 3 Synthesis of Mesogenic Compounds

Step 1: 4-Nonylbenzoyl chloride (15 g) was slowly added to a reactionflask containing a mixture of pyridine (110 mL) and hydroquinone (33.2g) and the resulting mixture was stirred for four hours, poured intowater (3 L) and the pH was adjusted to ˜3 with the slow addition of 12 NHCl. The resulting solution was extracted with hexane (200 mL). Theresulting hexane solution was washed with water, dried and concentrated.Methanol (100 mL) was added and the undesirable solid byproduct thatformed was filtered off. The methanol solution was collected,concentrated and dried. White solid (17 g) was obtained as the product.NMR showed that the product had a structure consistent with4-hydroxyphenyl 4-nonylbenzoate.

Step 2: To a reaction flask was added 4-hydroxyphenyl 4-nonylbenzoatefrom Step 1 (9.22 g), 4-(6-(tetrahydro-2H-pyran-2-yloxy)hexyloxy)benzoicacid (7.94 g) from Step 5 of Example 1, N,N′-dicyclohexylcarbodiimide(6.1 g), 4-dimethylaminopyridine (0.3 g) and methylene chloride (100mL). The mixture was stirred at room temperature for 24 hours. The solidbyproduct that formed was filtered off. The resulting solution wasconcentrated until solids started to form. Methanol (100 mL) was addedto further crystallization of the product. White crystals were collectedby vacuum filtration and dried (13.41 g). NMR showed that the producthad a structure consistent with 4-((4-nonylbenzoyl)oxy)phenyl4-((6-((tetrahydro-2H-pyran-2-yl)oxy)hexyl)oxy)benzoate.

Step 3: To a reaction flask was added product from Step 2 (13.41 g),methanol (80 mL), chloroform (200 mL) and pyridinium p-toluenesulfonate(0.52 g). The mixture was refluxed for six hours and then concentrated.Methanol (200 mL) was added. The resulting white solid (11 g) wascollected as the product. NMR showed that the product had a structureconsistent with4-((4-((6-hydroxyhexyl)oxy)benzoyl)oxy)phenyl-4-nonylbenzoate.

Step 4: To a reaction flask was added the product from Step 3 (5.56 g),succinic anhydride (1.98 g), DMAP (0.04 g) and THF (100 mL). Theresulting mixture was refluxed for 4 hours and poured into water (1 L).The precipitate that formed was collected and purified by silica columnseparation using a mixture of ethyl acetate/hexane (515 v/v). A whitesolid (5.77 g) was obtained as the product. NMR showed that the producthad a structure consistent with4-((6-(4-((4-((4-nonylbenzoyl)oxy)phenoxy)carbonyl)phenoxy)hexyl)oxy)-4-oxobutanoicacid.

Step 5: To a reaction flask was added the product from Step 4 (4 g),poly(hexamethylene carbonate) diol (1.7 g, M_(n) 860, Aldrich cataloguenumber 461172), N,N′-dicyclohexylcarbo-diimide (1.26 g),4-dimethylaminopyridine (0.06 g) and methylene chloride (20 mL). Themixture was stirred at room temperature for 24 hours. The solidbyproduct that formed was filtered off. The resulting mixture was pouredinto a mixture of water (3 L) and sodium bicarbonate (10 g) and stirredfor another 24 hours. Methylene chloride (200 mL) was added. Theseparated organic layer was collected, dried over magnesium sulfate andconcentrated. The recovered solid was stirred in methanol for 2 hours. Awhite solid was collected and dried as the product (3 g). NMR showedthat the product had a structure consistent with1-{(6-(6-(6-(6-(6-(6-(6-(4-(6-(4-(4-(4-nonylbenzoyloxy)phenoxycarbonyl)phenoxy)hexyloxy)-4-oxobutanoyloxy)hexyloxy)-6-carbonyloxyhexyloxy)-6-carbonyloxyhexyloxy)-6-carbonyloxyhexyloxy)-6-carbonyloxyhexyloxy)-6-carbonyloxyhexyloxy)-6-carbonyloxyhexyloxy}-4-{6-(4-(6-(4-(4-(4-nonylbenzoyloxy)phenoxycarbonyl)phenoxy)hexyloxyl}butane-1,4-dione.

Example 4

A photopolymerizable composition was prepared by combining a solventmixture with a composition comprising mesogenic compounds. The contentof the two compositions are described in Table 1 and in Table 2,respectively.

TABLE 1 Solvent mixture. Component Weight % Weight (g) BYK ®-322¹ 0.100.2 Methylethyl hydroquinone 0.15 0.3 Anisole 99.75 199.5 Total 100.00200.0 ¹Available from BYK-Chemie GmbH.

TABLE 2 Photopolymerizable liquid crystal composition. Component Weight% Weight (g) Solvent mixture 40 200 Mesogenic Compound (1) 24 120Mesogenic Compound (4) 24 120 Mesogenic Compound (5) 6 30 MesogenicCompound (6) 6 30 Total 100 500 Photoinitiator (Irgacure ® 819)⁵ 0.9 4.5Magnesium sulfate¹ 10 50 ¹Available from EMD Chemicals Inc.

A solvent blend of anisole (199.5 g), monomethyl ether hydroquinone(MEHQ) (0.3 g), and BYK®-322 (aralkyl-modified polymethylalkylsiloxane,0.2 g) were combined and heated to 90° C. Polymerizable mesogenicmonomers, Compound (1) (120 g), Compound (4) (120 g), Compound (5) (30g), and Compound (6) (30 g) were then added to the solvent blend. Themixture was stirred for at least 30 min until complete dissolution. Aphotoinitiator Irgacure® 819 (4.5 g) (BASF) was then added to themixture and allowed to dissolve for 30 min at 50° C., after which timemagnesium sulfate (50 g) was added, and the mixture stirred for anadditional 30 min. The mixture was then filtered using a 5 micronsyringe filter to obtain a clear filtrate.

Substrates were prepared by depositing a thin layer of indium tin oxide(ITO) on the surface of polyethylene terephthalate (PET). Substrates(ITO-coated PET; Sigma Aldrich) were pretreated with polyvinyl alcoholand aligned using specialized felt (Brewer Science, Inc.). The filteredsolution was then spin-coated onto the aligned pre-treated substrates toa thickness of 20 μm using a spin coater (Brewer Science, Inc.; Cee®300X). The spin-coated layer was baked at 50° C. for 30 min to removesolvent and then cured using a Fusion AETEK UV unit (Fusion Aetek UVSystems, Inc.). The UV unit included a single fusion lamp that providedan output of UVA at 0.359 W/cm², UVB at 0.361 W/cm², and UVC at 0.055W/cm² at an 8-inch lamp height.

A setup was fabricated to measure flexoelectric response. A test samplewas held horizontally by the two chucks and placed over two bladesspaced about 1 inch apart. To measure flexure a blade attached to anInstron machine was pushed onto the test sample between the lowerblades.

Test samples were prepared by sputtering an ITO electrode over the curedlayer of dielectric material. An electrode was interconnected to theupper and lower surfaces of the test sample and the electricalproperties measured while stress was applied.

The dielectric layers were tested at low forces at frequencies from 0.1Hz to 10 Hz.

The results are presented in Table 2 and in Table 3.

TABLE 3 Flexoelectric test results. Flexoelectric Test LCE S2 0.001%strain Frequency V_(PP) ¹ (V) F_(PP) ² (N) V/F³ 0.1 Hz 0.0865 0.05231.654 0.5 Hz 0.1006 0.0667 1.677   1 Hz 0.1105 0.0648 1.705   2 Hz0.1132 0.0667 1.697   5 Hz 0.1101 0.0383 2.875  10 Hz 0.086 0.0515 1.668¹V_(PP)—peak to peak voltage (volt). ²F_(PP)—peak to peak force(Newton). ³V/F—ratio V_(PP)/F_(PP).

TABLE 4 Flexoelectric test results. LCR Meter Permittivity (0.005%Strain) Fre- strain quency Permittivity E_(PP) ¹ P² gra- μ₁₂ μ₁₂ ⁴ (Hz)(F/m) (V/m) (C/m²) dient³ (C/m) (nC/m) 0.1 3.50E−11 11318 2.96E−07 0.963.08E−07 308 0.5 3.50E−11 12209 3.19E−07 0.96 3.33E−07 333 1 3.50E−1112939 3.38E−07 0.96 3.52E−07 352 2 3.50E−11 13219 3.46E−07 0.96 3.60E−07360 5 3.50E−11 12635 3.30E−07 0.96 3.44E−07 344 10 3.50E−11 114092.98E−07 0.96 3.11E−07 311 ¹Epp - electric field. ²P - flexoelectricpolarization. ³strain gradient. ⁴μ₁₂ - flexoelectric coefficient.

The flexoelectric coefficient μ₁₂ for flexoelectric materials typicallyrange from nC/m to μC/m, and the flexoelectric coefficient μ₁₂calculated for the liquid crystal layers was on the order of 0.3 μC/m.

Example 5 Prototype Assembly A

X-Bond® 4000 (corrosion inhibitor available from PPG Industries)pretreated aluminum was used as the substrate. To prepare the substrate,the substrate surface rub aligned with felt, and the dielectriccomposition of Example 4 was spin coated onto the aligned surface to athickness of 20 μm and UV cured. Polycarbonate bus ink P100889 wasapplied to the surface of the cured dielectric layer to provide an upperelectrode. Silver ink, XPVS-76980 (PPG Industries, Inc.) was applied tothe upper surface of the substrate to provide the lower electrode. Acopper tape lead was adhered to the silver ink, and another copper tapewas adhered to the upper surface of the aluminum substrate. The devicewas connected to an oscilloscope (Tektronix TDS 2002) for measurement ofthe voltage response.

Flexoelectric and potentially piezoelectric effects were determined formultiple devices. The flexoelectric response is shown in FIG. 1 forthree-point bending on an aluminum substrate with 0.01% strain at 2 Hz.The dielectric layer was characterized by a V_(pp) of 430 mV, at a forceof 4.6 N. In comparison, a PVDF-TrFe(polyvinyledenedifluoride-trifluoroethylene copolymer) film exhibited aV_(pp) of 580 mV at a force of 4.6 N.

The flexoelectric and piezoelectric properties of the dielectric layerswere comparable to that of a PVDF-TrFE thermoplastic film.

Example 6 Prototype Assembly B

A polyethylene terephthalate (PET) sheet with a coating of indium tinoxide (ITO) was used as a substrate. The ITO film was pretreated withplasma for 5 min before being rubbed and coated with the dielectriccomposition of Example 4 and then UV cured. Good alignment was achievedwhen visually examined using a polarized light source.

To fabricate the test structure, a second plasma cleaned ITO-PETelectrode was placed over the first dielectric layer and pressed firmlytogether. Copper tape leads were adhered to both ITO films, and thedielectric device was tested using an oscilloscope (Tektronix TDS 2002).As shown by comparing FIG. 2A and FIG. 2B a voltage response wasobserved when the device was tapped and/or distorted and theflexoelectric effect measured. FIG. 2A shows the signal before tappingthe device, and FIG. 2B shows the signal when the device was tapped.

Aspects of the Invention

Aspect 1. A polymerizable composition, comprising: a solvent; and acombination of polymerizable mesogenic monomers.

Aspect 2. The polymerizable composition of aspect 1, further comprisinga photoinitiator, a thermal initiator, or a combination thereof.

Aspect 3. The polymerizable composition of any one of aspects 1 to 2,wherein the combination of polymerizable mesogenic monomers comprises acombination of photopolymerizable mesogenic monomers or a combination ofthermally-activated polymerizable mesogenic monomers.

Aspect 4. The polymerizable composition of any one of aspects 1 to 3,wherein the combination of polymerizable mesogenic monomers comprises acompound of Formula (1):

P-(L)_(w)-(M¹-X)_(z)   (1)

wherein,

-   -   a) each X is independently:        -   i) a group —R;        -   ii) a group represented by -(L)_(y)-R;        -   iii) a group represented by -(L)-R;        -   iv) a group represented by -(L)_(w)-Q;        -   v) a group represented by a moiety of Formula (2):

-(L)^(y)-M²-(L)_(w)-P   (2)

-   -   -   vi) a group represented by -(L)_(y)-P; or        -   vii) a group represented by -(L)_(w)-[(L)_(w)-P]_(y);

    -   b) P comprises a reactive group;

    -   c) Q is selected from hydroxyl, amine, alkenyl, alkynyl, azido,        silyl, silylhydride, oxy(tetrahydro-2H-pyran-2-yl), thiol,        isocyanato, thioisocyanato, acryloxy, methacryloxy,        2-(acryloxy)ethylcarbamyl, 2-(methacryloxy)ethylcarbamyl,        aziridinyl, allylcarbonate, epoxy, carboxylic acid, carboxylic        ester, amide, carboxylic anhydride, and acyl halide;

    -   d) each L is independently selected from a single bond, a        polysubstituted, monosubstituted, unsubstituted or branched        spacer independently comprising aryl, (C₁₋₃₀)alkyl,        (C₁₋₃₀)alkylcarbonyloxy, (C₁₋₃₀)alkylamino, (C₁₋₃₀)alkoxy,        (C₁₋₃₀)perfluoroalkyl, (C₁₋₃₀)perfluoroalkoxy,        (C₁₋₃₀)alkylsilyl, (C₁₋₃₀)dialkylsiloxyl, (C₁₋₃₀)alkylcarbonyl,        (C₁₋₃₀)alkoxycarbonyl, (C₁₋₃₀)alkylcarbonylamino,        (C₁₋₃₀)alkylaminocarbonyl, (C₁₋₃₀)alkylcarbonate,        (C₁₋₃₀)alkylaminocarbonyloxy, (C₁₋₃₀)alkylaminocarbonylamino,        (C₁₋₃₀)alkylurea, (C₁₋₃₀)alkylthiocarbonylamino,        (C₁₋₃₀)alkylaminocarbonylthio, (C₂₋₃₀)alkene, (C₁₋₃₀)thioalkyl,        (C₁₋₃₀)alkylsulfone, or (C₁₋₃₀)alkylsulfoxide, wherein each        substituent is independently chosen from (C₁₋₅)alkyl,        (C₁₋₅)alkoxy, fluoro, chloro, bromo, cyano, (C₁₋₅)alkanoate        ester, isocyanato, thioisocyanato, and phenyl;

    -   e) R is selected from hydrogen, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy, C₁₋₁₈        alkoxycarbonyl, C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, poly(C₁₋₁₈        alkoxy), and a straight-chain or branched C₁₋₁₈ alkyl group that        is unsubstituted or substituted with cyano, fluoro, chloro,        bromo, or C₁₋₁₈ alkoxy, or poly-substituted with fluoro, chloro,        or bromo; and

    -   f) each of M¹ and M² independently comprises a rigid straight        rod-like liquid crystal group, a rigid bent rod-like liquid        crystal group, or a rigid disc-like liquid crystal group;

    -   wherein,        -   w is an integer from 1 to 26;        -   y is an integer from 2 to 25; and        -   z is 1 or 2;

    -   provided that when,        -   X is R, then w is an integer from 2 to 25, and z is 1;        -   X is -(L)_(y)-R, then w is 1, y is an integer from 2 to 25,            and z is 1;        -   X is -(L)-R, then w is an integer from 3 to 26, and z is 2;        -   X is -(L)_(w)-Q; then if P is represented by the group Q,            then w is 1, and z is 1; and if P is other than the group Q,            then each w is independently an integer from 1 to 26 and z            is 1;        -   X is a moiety of Formula (2), -(L)_(y)-M²-(L)_(w)-P, then w            is 1, y is an integer from 2 to 25, and z is 1;        -   X is -(L)_(y)-P, then w is 1, y is an integer from 2 to 25,            and z is 1 and -(L)_(y)- comprises a linear sequence of at            least 25 bonds between the mesogen and P; and        -   X is -(L)_(w)-[(L)_(w)-P]_(y), then each w is independently            an integer from 1 to 25, y is an integer from 2 to 6, and z            is 1.

Aspect 5. The polymerizable composition of aspect 4, wherein thephoto-activated group or thermally-activated group comprises an acrylateor a methacrylate.

Aspect 6. The polymerizable composition of any one of aspects 1 to 5,wherein the combination of polymerizable mesogenic monomers comprises:at least one polymerizable mesogenic monomer comprising twopolymerizable reactive groups; and at least one polymerizable mesogenicmonomer comprising one polymerizable reactive group.

Aspect 7. The polymerizable composition of aspect 6, wherein a molarratio of the at least one polymerizable mesogenic monomer comprising twopolymerizable reactive groups to the at least one polymerizablemesogenic monomer comprising one polymerizable reactive group is withina range from 1.5:1 to 1:1.

Aspect 8. The polymerizable composition of any one of aspects 1 to 7,wherein the combination of polymerizable mesogenic monomers comprise2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate) (Compound(1)); 4-methoxyphenyl 4-((6-(acryloyloxy)hexyl)oxy)benzoate (Compound(2)); 2-methyl-1,4-phenylenebis(4-((4-(acryloyloxy)butoxy)carbonyl)oxy)benzoate) (Compound (3));4-((4-((8-((6-methacryloyloxy)hexanoyl)oxy)octyl)oxy)benzoyl)oxy)phenyl4-methylbenzoate n=8 (Compound (4));4-((4-((8-((6-methacryloyloxy)hexanoyl)oxy)octyl)oxy)benzoyl)oxy)phenyl4-methylbenzoate n=3 (Compound (5));4-((4-pentylcyclohexane-1-carbonyl)oxy)phenyl4-((6-(acryloyloxy)hexyl)oxy)benzoate (Compound (6));3-(3,6-difluoro-4-(4′-propyl-[1,1′-bi(cyclohexan))]-4-yl)phenoxy)propylacrylate (Compound (7)); or a combination of any of the foregoing.

Aspect 9. A dielectric device comprising a dielectric layer, wherein thedielectric layer is prepared from the polymerizable composition of anyone of aspects 1 to 8.

Aspect 10. The dielectric device of aspect 9, wherein the dielectricdevice comprises a flexoelectric device, a piezoelectric device, or acombination thereof.

Aspect 11. The dielectric device of any one of aspects 9 to 10, whereinthe dielectric device comprises: the dielectric layer; a first electrodeinterconnected to the dielectric layer; and a second electrodeinterconnected to the dielectric layer.

Aspect 12. The dielectric device of any one of aspects 9 to 11, wherein,the first electrode comprises a first electrically conductive layer; thedielectric layer overlies the first electrically conductive layer; thesecond electrode comprise a second electrically conductive layer; andthe second electrically conductive layer overlies the dielectric layer.

Aspect 13. The dielectric device of any one of aspects 9 to 12, whereinthe dielectric layer is characterized by a thickness from 1 μm to 100μm.

Aspect 14. A part comprising the dielectric device of any one of aspects9 to 13.

Aspect 15. A method of preparing a dielectric layer, comprising:aligning a surface; applying the polymerizable composition of claim 1 tothe aligned surface, wherein the polymerizable composition comprises acombination of polymerizable mesogenic monomers; allowing the appliedcombination of polymerizable mesogenic monomers to align; andpolymerizing the aligned combination of polymerizable mesogenic monomersto form a dielectric layer.

Aspect 16. The method of aspect 15, wherein aligning comprises rubbingthe surface.

Aspect 17. The method of any one of aspects 15 to 16, wherein allowingthe applied combination of polymerizable mesogenic monomers to aligncomprises allowing the applied combination of polymerizable mesogenicmonomers to self-align.

Aspect 18. The method of any one of aspects 15 to 17, wherein thecombination of polymerizable mesogenic monomers comprises a combinationof photopolymerizable mesogenic monomers, or a combination ofthermally-initiated polymerizable mesogenic monomers.

Aspect 19. The method of any one of aspects 15 to 18, wherein thecombination of polymerizable mesogenic monomers comprises a compound ofFormula (1):

P-(L)_(w)-(M¹-X)_(z)   (1)

wherein,

-   -   a) each X is independently:        -   i) a group —R;        -   ii) a group represented by -(L)_(y)-R;        -   iii) a group represented by -(L)-R;        -   iv) a group represented by -(L)_(w)-Q;        -   v) a group represented by a moiety of Formula (2):

-(L)^(y)-M²-(L)_(w)-P   (2)

-   -   -   vi) a group represented by -(L)_(y)-P; or        -   vii) a group represented by -(L)_(w)-[(L)_(w)-P]_(y);

    -   b) P comprises a reactive group;

    -   c) Q is selected from hydroxyl, amine, alkenyl, alkynyl, azido,        silyl, silylhydride, oxy(tetrahydro-2H-pyran-2-yl), thiol,        isocyanato, thioisocyanato, acryloxy, methacryloxy,        2-(acryloxy)ethylcarbamyl, 2-(methacryloxy)ethylcarbamyl,        aziridinyl, allylcarbonate, epoxy, carboxylic acid, carboxylic        ester, amide, carboxylic anhydride, or acyl halide;

    -   d) each L is independently selected from a single bond, a        polysubstituted, monosubstituted, unsubstituted or branched        spacer independently comprising aryl, (C₁₋₃₀)alkyl,        (C₁₋₃₀)alkylcarbonyloxy, (C₁₋₃₀)alkylamino, (C₁₋₃₀)alkoxy,        (C₁₋₃₀)perfluoroalkyl, (C₁₋₃₀)perfluoroalkoxy,        (C₁₋₃₀)alkylsilyl, (C₁₋₃₀)dialkylsiloxyl, (C₁₋₃₀)alkylcarbonyl,        (C₁₋₃₀)alkoxycarbonyl (C₁₋₃₀)alkylcarbonylamino,        (C₁₋₃₀)alkylaminocarbonyl (C₁₋₃₀)alkylcarbonate,        (C₁₋₃₀)alkylaminocarbonyloxy, (C₁₋₃₀)alkylaminocarbonylamino,        (C₁₋₃₀)alkylurea, (C₁₋₃₀)alkylthiocarbonylamino,        (C₁₋₃₀)alkylaminocarbonylthio, (C₂₋₃₀)alkene, (C₁₋₃₀)thioalkyl,        (C₁₋₃₀)alkylsulfone, or (C₁₋₃₀)alkylsulfoxide, wherein each        substituent is independently chosen from (C₁₋₅)alkyl,        (C₁₋₅)alkoxy, fluoro, chloro, bromo, cyano, (C₁₋₅)alkanoate        ester, isocyanato, thioisocyanato, or phenyl;

    -   e) R is selected from hydrogen, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy, C₁₋₁₈        alkoxycarbonyl, C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, poly(C₁₋₁₈        alkoxy), or a straight-chain or branched C₁₋₁₈ alkyl group that        is unsubstituted or substituted with cyano, fluoro, chloro,        bromo, or C₁₋₁₈ alkoxy, or poly-substituted with fluoro, chloro,        or bromo; and

    -   f) each of M¹ and M² independently comprise a rigid straight        rod-like liquid crystal group, a rigid bent rod-like liquid        crystal group, or a rigid disc-like liquid crystal group;

    -   wherein,        -   w is an integer from 1 to 26;        -   y is an integer from 2 to 25; and        -   z is 1 or 2;

    -   provided that when,        -   X is R, then w is an integer from 2 to 25, and z is 1;        -   X is -(L)_(y)-R, then w is 1, y is an integer from 2 to 25,            and z is 1;        -   X is -(L)-R, then w is an integer from 3 to 26, and z is 2;        -   X is -(L)_(w)Q; then if P is represented by the group Q,            then w is 1, and z is 1; and if P is other than the group Q,            then each w is independently an integer from 1 to 26 and z            is 1;        -   X is a moiety of Formula (2), -(L)_(y)-M²-(L)_(w)-P, then w            is 1, y is an integer from 2 to 25, and z is 1;        -   X is -(L)_(y)-P, then w is 1, y is an integer from 2 to 25,            and z is 1 and (L)_(y)- comprises a linear sequence of at            least 25 bonds between the mesogen and P; and        -   X is -(L)_(w)-[(L)_(w)-P]_(y), then each w is independently            an integer from 1 to 25, y is an integer from 2 to 6, and z            is 1.

Aspect 20. The method of aspect 19, wherein the reactive group comprisesan acrylate or a methacrylate.

Aspect 21. The method of any one of aspects 15 to 20, wherein thecombination of polymerizable mesogenic monomers comprises: at least onepolymerizable mesogenic monomer comprising two polymerizable reactivegroups; and at least one polymerizable mesogenic monomer comprising onepolymerizable reactive group.

Aspect 22. The method of aspect 21, wherein a molar ratio of the atleast one polymerizable mesogenic monomer comprising two polymerizablereactive groups to the at least one polymerizable mesogenic monomercomprising one polymerizable reactive group is within a range from 1.5:1to 1:1.

Aspect 23. The method of any one of aspects 15 to 22, wherein thecombination of polymerizable mesogenic monomers comprises2-methyl-1,4-phenylene bis(4-(3-(acryloyloxy)propoxy)benzoate) (Compound(1)); 4-methoxyphenyl 4-((6-(acryloyloxy)hexyl)oxy)benzoate (Compound(2)); 2-methyl-1,4-phenylenebis(4-((4-(acryloyloxy)butoxy)carbonyl)oxy)benzoate) (Compound (3));4-((4-((8-((6-methacryloyloxy)hexanoyl)oxy)octyl)oxy)benzoyl)oxy)phenyl4-methylbenzoate n=8 (Compound (4));4-((4-((8-((6-methacryloyloxy)hexanoyl)oxy)octyl)oxy)benzoyl)oxy)phenyl4-methylbenzoate n=3 (Compound (5));4-((4-pentylcyclohexane-1-carbonyl)oxy)phenyl4-((6-(acryloyloxy)hexyl)oxy)benzoate (Compound (6));3-(3,6-difluoro-4-(4′-propyl-[1,1′-bi(cyclohexan))]-4-yl)phenoxy)propylacrylate (Compound (7)); or a combination of any of the foregoing.

Aspect 24. The method of any one of aspects 15 to 23, whereinpolymerizing the aligned combination of polymerizable mesogenic monomerscomprises irradiating the applied composition with ultravioletradiation, or heating the applied composition.

Aspect 25. A dielectric layer prepared by the method of any one ofaspects 15 to 24.

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive.Furthermore, the claims are not to be limited to the details givenherein, and are entitled to their full scope and equivalents thereof.

1-20. (canceled)
 21. A dielectric layer comprising polymerized mesogenicmonomers, wherein the polymerized mesogenic monomers comprise acombination of mesogenic monomers having the structure of Formula (1):P-(L)_(w)-(M¹-X)_(z)   (1) wherein, a) each —X is independently: i) agroup —R; ii) a group represented by -(L)_(y)-R; iii) a grouprepresented by -(L)-R; iv) a group represented by -(L)_(w)-Q; v) a grouprepresented by a moiety of Formula (2):-(L)^(y)-M²-(L)_(w)-P (2) vi) a group represented by -(L)_(y)-P; or vii)a group represented by -(L)_(w)-[(L)_(w)-P]_(y); b) P comprises areactive group; c) Q is selected from hydroxyl, amine, alkenyl, alkynyl,azido, silyl, silylhydride, oxy(tetrahydro-2H-pyran-2-yl), thiol,isocyanato, thioisocyanato, acryloxy, methacryloxy,2-(acryloxy)ethylcarbamyl, 2-(methacryloxy)ethylcarbamyl, aziridinyl,allylcarbonate, epoxy, carboxylic acid, carboxylic ester, amide,carboxylic anhydride, and acyl halide; d) each L is independentlyselected from a single bond, a polysubstituted, monosubstituted,unsubstituted or branched spacer independently comprising aryl,(C₁₋₃₀)alkyl, (C₁₋₃₀)alkylcarbonyloxy, (C₁₋₃₀)alkylamino, (C₁₋₃₀alkoxy,(C₁₋₃₀)perfluoroalkyl, (C₁₋₃₀)perfluoroalkoxy, (C₁₋₃₀)alkylsilyl,(C₁₋₃₀)dialkylsiloxyl, (C₁₋₃₀)alkylcarbonyl, (C₁₋₃₀)alkoxycarbonyl,(C₁₋₃₀)alkylcarbonylamino, (C₁₋₃₀)alkylaminocarbonyl,(C₁₋₃₀)alkylcarbonate, (C₁₋₃₀)alkylaminocarbonyloxy,(C₁₋₃₀)alkylaminocarbonylamino, (C₁₋₃₀)alkylurea,(C₁₋₃₀)alkylthiocarbonylamino, (C₁₋₃₀)alkylaminocarbonylthio,(C₂₋₃₀)alkene, (C₁₋₃₀)thioalkyl, (C₁₋₃₀)alkylsulfone, or(C₁₋₃₀)alkylsulfoxide, wherein each substituent is independently chosenfrom (C₁₋₅)alkyl, (C₁₋₅)alkoxy, fluoro, chloro, bromo, cyano,(C₁₋₅)alkanoate ester, isocyanato, thioisocyanato, and phenyl; e) R isselected from hydrogen, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy, C₁₋₁₈ alkoxycarbonyl,C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, poly(C₁₋₁₈ alkoxy), and astraight-chain or branched C₁₋₁₈ alkyl group that is unsubstituted orsubstituted with cyano, fluoro, chloro, bromo, or C₁₋₁₈ alkoxy, orpoly-substituted with fluoro, chloro, or bromo; and f) each of M¹ and M²independently comprises a rigid straight rod-like liquid crystal group,a rigid bent rod-like liquid crystal group, or a rigid disc-like liquidcrystal group; wherein, w is an integer from 1 to 26; y is an integerfrom 2 to 25; and z is 1 or 2; provided that when, X is R, then w is aninteger from 2 to 25, and z is 1; X is -(L)_(y)-R, then w is 1, y is aninteger from 2 to 25, and z is 1; X is -(L)-R, then w is an integer from3 to 26, and z is 2; X is -(L)_(w)-Q; then if P is represented by thegroup Q, then w is 1, and z is 1; and if P is other than the group Q,then each w is independently an integer from 1 to 26 and z is 1; X is amoiety of Formula (2), -(L)_(y)-M²-(L)_(w)-P, then w is 1, y is aninteger from 2 to 25, and z is 1; X is -(L)_(y)-P, then w is 1, y is aninteger from 2 to 25, and z is 1 and (L)_(y)- comprises a linearsequence of at least 25 bonds between the mesogen and P; and X is-(L)_(w)-[(L)_(w)-P]_(y), then each w is independently an integer from 1to 25, y is an integer from 2 to 6, and z is
 1. 22. The dielectric layerof claim 21, wherein the photo-activated group or thermally-activatedgroup comprises an acrylate or a methacrylate.
 23. The dielectric layerof claim 21, further comprising a photoinitiator, a thermal initiator,or a combination thereof.
 24. The dielectric layer of claim 21, whereinthe combination of mesogenic monomers comprises a combination ofphotopolymerizable mesogenic monomers or a combination ofthermally-activated polymerizable mesogenic monomers.
 25. The dielectriclayer of claim 21, wherein the combination of mesogenic monomerscomprises: at least one polymerizable mesogenic monomer comprising twopolymerizable reactive groups; and at least one polymerizable mesogenicmonomer comprising one polymerizable reactive group.
 26. The dielectriclayer of claim 25, wherein a molar ratio of the at least onepolymerizable mesogenic monomer comprising two polymerizable reactivegroups to the at least one polymerizable mesogenic monomer comprisingone polymerizable reactive group is within a range from 1.5:1 to 1:1.27. The dielectric layer of claim 21, wherein the combination ofmesogenic monomers comprise 2-methyl-1,4-phenylenebis(4-(3-(acryloyloxy)propoxy)benzoate) (Compound (1)); 4-methoxyphenyl4-((6-(acryloyloxy)hexyl)oxy)benzoate (Compound (2));2-methyl-1,4-phenylenebis(4-((4-(acryloyloxy)butoxy)carbonyl)oxy)benzoate) (Compound (3));4-((4-((8-((6-methacryloyloxy)hexanoyl)oxy)octyl)oxy)benzoyl)oxy)phenyl4-methylbenzoate n=8 (Compound (4));4-((4-((8-((6-methacryloyloxy)hexanoyl)oxy)octyl)oxy)benzoyl)oxy)phenyl4-methylbenzoate n=3 (Compound (5));4-((4-pentylcyclohexane-1-carbonyl)oxy)phenyl4-((6-(acryloyloxy)hexyl)oxy)benzoate (Compound (6));3-(3,6-difluoro-4-(4′-propyl-[1,1′-bi(cyclohexan))]-4-yl)phenoxy)propylacrylate (Compound (7)); or a combination of any of the foregoing. 28.The dielectric layer of claim 21, wherein the dielectric layer comprisesa coating.
 29. The dielectric layer of claim 21, wherein the dielectriclayer comprises a film.
 30. The dielectric layer of claim 21, whereinthe dielectric layer exhibits piezoelectric properties.
 31. Thedielectric layer of claim 21, wherein the dielectric layer exhibitsflexoelectric properties.
 32. A dielectric device comprising thedielectric layer of claim
 21. 33. The dielectric device of claim 32,wherein the device comprises a piezoelectric device, a flexoelectricdevice of a combination thereof.
 34. The dielectric device of claim 32,wherein, the device comprises: a substrate; and the dielectric layeroverlies the substrate.
 35. The dielectric device of claim 32, whereinthe device comprises: a first layer; the dielectric layer overlying thefirst layer; and a second layer overlying the dielectric layer.
 36. Amethod of preparing the dielectric layer, comprising: aligning asurface; applying a composition comprising a combination ofpolymerizable mesogenic monomers to the aligned surface, wherein thepolymerizable mesogenic monomers has the structure of Formula (1):P-(L)_(w)-(M¹-X)_(z)   (1) wherein, a) each X is independently: i) agroup R; ii) a group represented by -(L)_(y)-R; iii) a group representedby -(L)-R; iv) a group represented by -(L)_(w)-Q; v) a group representedby a moiety of Formula (2):-(L)^(y)-M²-(L)_(w)-P   (2) vi) a group represented by -(L)_(y)-P; orvii) a group represented by -(L)_(w)-[(L)_(w)-P]_(y); b) P comprises areactive group; c) Q is selected from hydroxyl, amine, alkenyl, alkynyl,azido, silyl, silylhydride, oxy(tetrahydro-2H-pyran-2-yl), thiol,isocyanato, thioisocyanato, acryloxy, methacryloxy,2-(acryloxy)ethylcarbamyl, 2-(methacryloxy)ethylcarbamyl, aziridinyl,allylcarbonate, epoxy, carboxylic acid, carboxylic ester, amide,carboxylic anhydride, and acyl halide; d) each L is independentlyselected from a single bond, a polysubstituted, monosubstituted,unsubstituted or branched spacer independently comprising aryl,(C₁₋₃₀)alkyl, (C₁₋₃₀)alkylcarbonyloxy, (C₁₋₃₀)alkylamino, (C₁₋₃₀)alkoxy,(C₁₋₃₀)perfluoroalkyl, (C₁₋₃₀)perfluoroalkoxy, (C₁₋₃₀)alkylsilyl,(C₁₋₃₀)dialkylsiloxyl, (C₁₋₃₀)alkylcarbonyl, (C₁₋₃₀)alkoxycarbonyl,(C₁₋₃₀)alkylcarbonylamino, (C₁₋₃₀)alkylaminocarbonyl,(C₁₋₃₀)alkylcarbonate, (C₁₋₃₀)alkylaminocarbonyloxy,(C₁₋₃₀)alkylaminocarbonylamino, (C₁₋₃₀)alkylurea,(C₁₋₃₀)alkylthiocarbonylamino, (C₁₋₃₀)alkylaminocarbonylthio,(C₂₋₃₀)alkene, (C₁₋₃₀)thioalkyl, (C₁₋₃₀)alkylsulfone, or(C₁₋₃₀)alkylsulfoxide, wherein each substituent is independently chosenfrom (C₁₋₅)alkyl, (C₁₋₅)alkoxy, fluoro, chloro, bromo, cyano,(C₁₋₅)alkanoate ester, isocyanato, thioisocyanato, and phenyl; e) R isselected from hydrogen, C₁₋₁₈ alkyl, C₁₋₁₈ alkoxy, C₁₋₁₈ alkoxycarbonyl,C₃₋₁₀ cycloalkyl, C₃₋₁₀ cycloalkoxy, poly(C₁₋₁₈ alkoxy), and astraight-chain or branched C₁₋₁₈ alkyl group that is unsubstituted orsubstituted with cyano, fluoro, chloro, bromo, or C₁₋₁₈ alkoxy, orpoly-substituted with fluoro, chloro, or bromo; and f) each of M¹ and M²independently comprises a rigid straight rod-like liquid crystal group,a rigid bent rod-like liquid crystal group, or a rigid disc-like liquidcrystal group; wherein, w is an integer from 1 to 26; y is an integerfrom 2 to 25; and z is 1 or 2; provided that when, X is R, then w is aninteger from 2 to 25, and z is 1; X is -(L)_(y)-R, then w is 1, y is aninteger from 2 to 25, and z is 1; X is -(L)-R, then w is an integer from3 to 26, and z is 2; X is -(L)_(w)-Q; then if P is represented by thegroup Q, then w is 1, and z is 1; and if P is other than the group Q,then each w is independently an integer from 1 to 26 and z is 1; X is amoiety of Formula (2), -(L)_(y)-M²-(L)_(w)-P, then w is 1, y is aninteger from 2 to 25, and z is 1; X is -(L)_(y)-P, then w is 1, y is aninteger from 2 to 25, and z is 1 and -(L)_(y)- comprises a linearsequence of at least 25 bonds between the mesogen and P; and X is-(L)_(w)-[(L)_(w)-P]_(y), then each w is independently an integer from 1to 25, y is an integer from 2 to 6, and z is
 1. allowing the appliedpolymerizable mesogenic monomers to align; and polymerizing the alignedpolymerizable mesogenic monomers to form a dielectric layer.
 37. Themethod of claim 36, wherein aligning comprises rubbing the surface. 38.The method of claim 36, wherein allowing the applied combination ofpolymerizable mesogenic monomers to align comprises allowing the appliedcombination of polymerizable mesogenic monomers to self-align.
 39. Adielectric layer prepared by the method of claim 36.